JP2004112694A - Color control method, color control apparatus, color conversion definition editing apparatus, image processing apparatus, program, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To partially control a color without damaging the gradation or continuity of the color in a method for converting the color of a certain color space coordinate system to another color on the same color space. <P>SOLUTION: A control target color space P0 including a movement target partial color space P1 including a color to be a target of conversion processing and a movement destination partial color space P2 including a converted color so as to be inscribed is handled as a conversion target area P. In the conversion target area P, a color point of a control target is moved to be overlapped on a color point after the movement toward a target color, and a boundary of the moving area is hard by moved or is not moved at all. Thus, a phenomenon such as color skipping or gradation inversion does hard by occur in the boundary portion with the outside of the control target area. Therefore, partial color control is performed while making compatible maintenance of continuity of gradation and prevention of inverse color conversion in an image as a color control target. <P>COPYRIGHT: (C)2004,JPO

Description

【００４０】
Ｘが区間ＡＤにある場合には、式（２）により移動ベクトルが決定できる。ただし、ＤＸは点Ｄと点Ｘの距離、ＡＤは点Ａと点Ｄの距離、“↑ＡＢ”は点Ａから点Ｂに向かうベクトル、“↑Ｐ”は点Ｘにおける移動ベクトルである。
【数２】

【００４１】
また、点Ｘの位置ベクトルを“↑ＡＸ”とし、移動後の位置ベクトルを“↑ＡＹ”とすると式（３）となる。
【数３】

【００４２】
前記は、移動対象点Ａで分割することにより、階調逆転の発生しない移動ベクトルあるいは移動量が求まることを意味する。また、式（１）におけるＣＸ／ＡＣや式（２）におけるＤＸ／ＡＤは、“０”から“１”に収まる値であり、点Ｘにおける移動量は最も単純な関係であるが、たとえば、（ＣＸ／ＡＣ）^２や（ＣＸ／ＡＣ）^１／２としてもよい。また、特に関数でなくとも単調な関係であれば、たとえばテーブル形式でデータを記憶しておき、その間は補間をするなどの手法を用いてもよい。
【００４３】
前記は、Ｘ軸上の１次元の移動規則を述べたものであるが、実際には、点Ｘは、調整対象領域中の任意の点である。点Ｘの座標値を（ｘ，ｙ，ｚ）とすると、調整対象領域ＰはＸ軸を回転軸とする回転体であるので、（ｘ，０，０）から（ｘ，ｙ，ｚ）への距離をＲ、調整対象領域Ｐの半径をｒとし、式（４）のように重みβを算出することができる。
【数４】

【００４４】
この式（４）も、たとえば（１−Ｒ／ｒ）^２にするなど、前記のＸ軸上の説明と同様な変形ができる。ここで、重みβと式（１）または式（２）の関係の説明をする。式（１）と式（２）をまとめて式（５）のように表現する。
【数５】

【００４５】
式（５）は、Ｘ軸上の関係式として説明してきたが、ｙ，ｚの要素を無視して任意の点Ｘで求めることができる。このとき、調整対象領域内の任意の点の移動ベクトルは式（６）となる。
【数６】

【００４６】
以上が円筒形の場合の説明である。調整対象領域のＸ軸と直交する端面が平面である場合は円筒と同様の考え方でよい。また、断面形状が楕円などで回転体でない場合も、同様にＡＣ、ＡＤが求まることは自明である。
【００４７】
図４は、調整対象領域Ｐがカプセル形状の場合における色調整について説明するものである。図示した例では、Ｘ−Ｚ平面にＡＣ，ＡＤを図示しており、太い実線がＡＣ（Ａの左側）、ＡＤ（Ａの右側）の例である。
【００４８】
カプセル形状では、円筒形などのような場合より多少複雑になるが、円筒形と同様の考え方が適用できる。この場合も回転体であるので、その領域内の点Ｘの座標値を（ｘ，ｙ，ｚ）、調整対象領域は（ｘ，０，０）から（ｘ，ｙ，ｚ）への距離をＲ、調整対象領域Ｐの半径をｒとする。Ｒに応じて、式（１）のＡＣ、式（２）のＡＤが変化するようにすればよい。
【００４９】
以上の説明は、移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２が包含関係にない場合でも調整対象領域内で階調逆転を起こさず、滑らかに移動を行なう原理を述べたものである。部分的な色調整を行なう場合、特に自然画像を対象とした場合は、階調逆転を起こさず、滑らかであることは重要であり、本方式は、これに合致するものである。
【００５０】
前記の例は、移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２が合同の関係にある場合について説明したものであるが、相似の関係であってもよい。
【００５１】
図５は、移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２が相似の関係にある場合における色調整について説明する図である。Ａを含むＸ軸に直交する調整対象領域境界までの半径をｒ１、Ｂを通りＸ軸に直交する調整対象慮域境界までの半径をｒ２、点Ｒ０を通りＸ軸に直交する調整対象慮域境界までの半径ｒ３、Ｘ軸と点Ｒ０との距離をＲ３とする。
【００５２】
図示した例は、移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２が、ともに円錐台の形状である。合同関係にある場合にはｒ１＝ｒ２であったが、相似関係にある場合ｒ１≠ｒ２となる。このため、移動ベクトルの向きが点Ｒ０に依存して、厳密にはＲ３に依存して変更しなければならない点が異なることになる。移動ベクトルの向きは、以下のように決める。
【００５３】
まず、Ｒ３／ｒ３＝Ｒ１／ｒ１＝Ｒ２／ｒ２となるように、Ｒ１、Ｒ２が決定できる。また、点Ｒ０により決定される移動ベクトルを“↑Ａ’Ｂ’”とすると、Ｘ軸と“↑Ａ’Ｂ’”は捻れの位置にならないように決定するのが妥当で、一意に“↑Ａ’Ｂ’”を決定できる。また、前記α、βの係数を掛ける前の移動ベクトルの大きさは、点Ｒ０の位置に関わらず、“↑Ａ’Ｂ’”のＸ軸方向の距離は｜ＡＢ｜とすればよく、このベクトルを基本移動ベクトルという。基本移動ベクトルは点Ｒ０の関数とみなすことができ、基本移動ベクトルを“↑Ｆ（ｘ）”と表記すると、式（７）により移動ベクトル“↑Ｐ”を求めることができる。
【数７】

【００５４】
このようにすれば、移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２が相似の関係であっても、基本移動ベクトルの向きがｘの関数となるのみで、基本的には、前述の移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２が合同の形状である場合と何ら変わりがない。
【００５５】
以上は、調整対象領域が回転体である場合についての説明であったが、たとえば、移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２が楕円体のような回転対象でない場合でも、前記の回転対象な合同、相似の形状のように取り扱うことができる。詳細を説明することは割愛するが、前記の半径ｒと距離Ｒが点Ｒ０（ｘ，ｙ，ｚ）において、合同の場合は点Ｘの要素ｙ，ｚの関数になり、相似の場合はｘ，ｙ，ｚの３要素の関数に拡張すればよい。また、前記説明では、基本移動ベクトル、係数α、βを最も簡単な関数で記述したが、これらは一例である。
【００５６】
基本移動ベクトルは交差しないようにすれば、前記以外の決定方法でもよい。また、α、βに関しては、両者の積が基本移動ベクトルにかかる係数とみなすことができ、最終的に、式（３）により移動後の色座標が決まる。このような観点からみると、ある基本移動ベクトル上の移動前の点列と、移動後の点列の順序が逆転しないように、α，βを決定する、または、直接α・βに相当する係数を決定する方法をとってもかまわない。
【００５７】
以上のように、上記方法により変換対象領域Ｐについて色調整を実施すれば、変換対象領域Ｐの中は、目標に向かって、調整対象の色点が移動後の色点に重なるように移動させ、移動領域の境界は殆ど移動しないあるいは全く移動しないようにしたので、調整対象領域外との境界部では色飛びや階調逆転などの現象が殆ど生じない。つまり、色調整対象の画像の階調の連続性維持と色逆転の防止を両立させて、部分的色調整を行なうことができる。
【００５８】
好ましい再現において、記憶色再現は重要である。色空間のある特定の色のみを変更する選択的色調整をする際には、上記手法が極めて有効である。たとえば、原稿を解析して特定の色領域、たとえば肌色をある色（記憶色）に変更することができれば、好ましい再現に付加価値を提供できる。また上記手法は、白点（Ｗｈｉｔｅ　Ｐｏｉｎｔ　）の補正など、色空間上で局所的に色を移動させたい場合に応用できるという利点がある。
【００５９】
従来の方法では、たとえば、色空間上、大きな楕円体から、この楕円体に完全に含まれる（内包関係にある）領域に存在する小さな楕円体への選択色調整の手法が提案されているが、内包関係にない位置関係の移動はできない、あるいは、無理に色調調整すれば原理的に階調逆転が起こるという問題がある。これに対して、上記手法によれば、たとえば球状の移動対象部分色空間Ｐ１と、同じく球状の移動先部分色空間Ｐ２とを結ぶ領域として画定される変換対象領域Ｐ内のみを調整対象色空間Ｐ０として取り扱うことで、内包関係の制約を取り外している。
【００６０】
このため、たとえば、移動したい色の中心と半径や移動先の中心と半径は独立に与えられ、調整の自由度が大きくなっている。そしてこれにより、自由度の高い選択的色調整機能が提供できる。色空間中で、特定領域の座標をある領域に移動する際、移動しない領域との境界の段差を考慮することができ、移動後の疑似輪郭や階調逆転などの画質欠陥が生じ難い。なお、領域の形状に関しては、球より楕円体の方が、自由度は高いが、算術的に一般解を求めることは難しい。
【００６１】
次に、画像データ中の下地除去などに有効な部分的色調整について、その原理を説明する。画像データ中の下地は、印刷物などであれば、インクの乗らない紙に対応する部位をさし、ＣＧ（コンピュータグラフィックス）などのようにデジタル的に生成されていない画像の場合、たとえば、原稿やシーンを撮像系を通して得られた場合に、本来下地であるべき部位が、ある程度のばらつきを持ってしまっている場合である。この方法を前記の部分的色調整と区別するために、収斂型部分的色調整ということにする。
【００６２】
図６は、収斂型部分的色調整について説明する図である。図６（Ａ）において、収斂型部分的色調整をするとは、図６（Ａ）における点Ａを中心とする小さい球体Ｓの領域内の点を全て点Ｂ一点に移動し、球体Ｓの外側は、連続性を保ったまま、部分的色調整を行なうことを意味する。この球体Ｓを収斂領域という。なお、図中球体Ｓよりも外側の球体とさらに外側との境界は、前述の部分的色調整により、その境界部で階調の不連続性や色逆転が生じないように色変換するのは上述の通りである。下地のバラツキの範囲が球体Ｓ内とすれば、全て下地は一定値にすることができ、その付近の色は連続性を保つことができるような移動を考える。収斂型部分的色調整は２段階に分けると分かり易い。
【００６３】
図６（Ｂ）に示すように、点Ａを中心とする小さい球体Ｓ、この球体Ｓの半径をＲ２、点Ａを中心とする大きな球（移動対象部分色空間Ｐ１）の半径Ｒ１、この大きな球に含まれる、移動を行なうべき点をＸ、ＡからＸまでの距離をｒとすると、ｒ＜Ｒ２であれば、Ｘは無条件に点Ａの座標値とすればよい。Ｒ２≦ｒ≦Ｒ１の領域では、ステップ１基本移動ベクトル（前記の部分的色調整の基本移動ベクトルと区別するためにこういう）の向きは、点Ｘから点Ａに向かうベクトルであり、長さは点Ｘから点Ａへの距離である。このステップ１基本移動ベクトルを“↑Ｖ１”とすると、式（８）によりステップ１移動ベクトル“↑Ｖ１”が求められる。
【数８】

【００６４】
式（８）において重みγを単純な関数で表現したが、点Ｘが球体Ｓの表面で“１”、移動対象部分色空間Ｐ１の表面で“０”である関係になるように、単調かつ、半径Ｒ１上の点列を移動して、それらを移動した後の点列の順序が入れ替わることがない関係であればよい。
【００６５】
点Ｘの位置ベクトルを“↑ＡＸ”として、移動後の位置ベクトルを“↑ＡＺ”とすると、点Ｘが移動される先は式（９）で表される。なお、点Ａは部分的色調整のときと同様に、原点に平行移動されているものであり“↑０”ベクトルである。
【数９】

【００６６】
また、このように“↑ＡＸ”が移動された“↑ＡＺ”を点Ｒ０’と表現する。この点Ｒ０’が求まったところで１段階が終了する。２段階目は、点Ｒ０’に対して前記の部分的色調整と全く同じ移動を行なえばよい。この２段階処理をまとめた形式で記述すると式（１０）で表現される。
【数１０】

【００６７】
以上が収斂型部分的色調整の原理の説明である。この収斂型部分的色調整の適用部分は本来の変換対象領域Ｐ内の一部であるので、調整対象領域外との境界部では色飛びや階調逆転などの現象が殆ど生じないのは前述の通りである。
【００６８】
また、部分的色調整、収斂方部分色調整とも、対象とする色空間が多次元である場合について述べたが、単色画像のような、いわゆる１次元の色空間であっても適用可能である。
【００６９】
図７は、上述の部分的色調整方法を実施する画像処理装置の一実施形態を示すブロック図である。上述のように、部分的色調整を行なう色空間はいかなる色空間でもかまわないが、本実施形態では、ＣＩＥで規定されるでＬ^＊ａ^＊ｂ^＊色空間とする。ただし、これに限定されるものではなく、たとえば赤Ｒ、緑Ｇ、および青Ｂ（纏めてＲＧＢという）を利用するディスプレイＲＧＢやスキャナＲＧＢなどのデバイス依存型の色空間、あるいはＣＩＥで規定されるＬ^＊ｕ^＊ｖ^＊表現のデバイスに依存しない色空間であるデバイス非依存型色空間上の色信号を使用することもできる。勿論、部分的色調整部２０は、これら以外の各種のデバイス依存色空間や各種のデバイス非依存色空間の何れを色調整対象の信号として取り扱ってもよい。
【００７０】
本実施形態の画像処理装置１は、たとえばＲＧＢ色区間で表された入力画像データを取り込む画像入力部３と、入力画像データの色信号ＳｉｎをＬ^＊ａ^＊ｂ^＊空間上の色信号に変換する色変換部１０と、移動対象部分色空間Ｐ１と移動先部分色空間Ｐ２とで画定される変換対象領域Ｐ内の各色点について、上述のようにして色座標を移動することで部分的色調整を実施する色座標移動部の一例である部分的色調整部２０と、この部分的色調整部２０における移動パラメータを設定する移動パラメータ設定部の一例である部分的色調整パラメータ取得部３０とを備える。
【００７１】
また画像処理装置１は、部分的色調整部２０により色調整されたＬ^＊ａ^＊ｂ^＊空間上の色信号を元のＲＧＢ色空間の色信号に戻す色変換部４０と、色変換部４０からの色信号を、たとえばプリンタやＣＲＴあるいはＬＣＤ（液晶）などの外部の画像出力機器の向けて出力する画像データ出力部５とを備える。
【００７２】
色変換部１０、部分的色調整部２０、部分的色調整パラメータ取得部３０、および色変換部４０により、本発明に係る色調整装置４００の一実施形態が構成される。
【００７３】
色変換部１０，４０における色変換処理は公知の技術であるので、詳細な説明を割愛する。部分的色調整部２０は、色変換係数を取得する係数取得部２２を有している。この係数取得部２２は、上述のように、色変換係数として、色座標の移動を示すベクトルの係数を取得する。
【００７４】
実際の部分的色調整に先立って、部分的色調整パラメータ取得部３０により部分的色調整に関わるパラメータを取得しておく。パラメータ取得に関しては後述する。部分的色調整に関わるパラメータは部分的色調整部２０にセットされる。また、実際の画像処理に先立って、色変換部１０に対して、入力画像をＬ^＊ａ^＊ｂ^＊色信号に変換するための色変換係数がセットされる。
【００７５】
また、色変換部４０は、色変換部１０による色変換の逆変換をセットしておくと、最終的に得られる出力画像は、部分的色調整による変更のみを行なった画像となる。また、部分的色調整を行なった後、プリンタに出力を行なうのであれば、プリンタ用ＣＭＹＫなどの色信号へ変換する色変換係数をセットしてもよく、また、部分的色調整後のＬ^＊ａ^＊ｂ^＊画像信号を残したければ、色変換部４０による色変換を行なわないことも選択でき、適宜の色変換係数をセットすればよい。
【００７６】
このように、準備を終えた後、画素順次で入力画像が、色変換部１０によりにＬ^＊ａ^＊ｂ^＊色信号に変換変換さる。次の部分的色調整部２０は、調整対象領域Ｐ内であれば、所望の調整を実行して調整したＬ^＊ａ^＊ｂ^＊色信号を、そうでなければ、部分的色調整部２０に入力されたＬ^＊ａ^＊ｂ^＊色信号をそのまま出力する。部分的色調整部２０の内部動作についての詳細は後述する。次に、色変換部４０で、所望の色変換がなされ、出力画像データが生成される。この出力画像データは、画像データ出力部５を介して表示装置や印刷装置などに向けて出力される。
【００７７】
図８は、本実施形態の画像処理装置１における部分的色調整部２０の詳細構成例を示すブロック図である。図示するように、部分的色調整部２０は、色変換部１０から入力されたＬ^＊ａ^＊ｂ^＊色信号が示す画素データが、１次領域の内部であるのか外部であるのかを判定する１次領域内外判定部２１０と、１次領域内外判定部２１０により内部（境界を含んでよい）であると判定された画素データについて、所定の平行移動や回転移動を実施する移動処理部２２０とを有する。移動処理部２２０にて移動処理されたＬ^＊ａ^＊ｂ^＊色信号を以下（Ｌ^＊ａ^＊ｂ^＊）１色信号という。また、平行移動や回転移動が施されていないＬ^＊ａ^＊ｂ^＊色信号を、以下（Ｌ^＊ａ^＊ｂ^＊）０色信号という。１次領域を対象とした平行移動や回転移動は、Ｌ^＊ａ^＊ｂ^＊の３軸空間におけるもので、周知の技術を用いればよい。ここでは、その詳細な説明を割愛する。
【００７８】
また部分的色調整部２０は、移動処理部２２０からの平行移動や回転移動が施された（Ｌ^＊ａ^＊ｂ^＊）１色信号と１次領域内外判定部２１０からの前記平行移動や回転移動が施されていない（Ｌ^＊ａ^＊ｂ^＊）０色信号とについて、各色信号が示す画素データが、変換対象領域Ｐの内部であるのか外部であるのかを判定する２次領域内外判定部２３０と、上述の部分色調整の原理に基づいて所望の部分色調整を実施する係数取得部２２を包含した部分色調整変換部２４０と、移動処理部２２０で行なわれた回転移動の逆変換や平行移動の逆変換を実施する移動逆変換処理部２５０とを備える。
【００７９】
２次領域内外判定部２３０は、内外判定を実施したときに外部であると判定した場合は、１次領域内外判定部２１０からの（Ｌ^＊ａ^＊ｂ^＊）０色信号をそのまま色変換部４０に出力する。一方、内部（境界部を含んでよい）であると判定したときには移動処理部２２０からの（Ｌ^＊ａ^＊ｂ^＊）１色信号を部分色調整変換部２４０に送出する。部分色調整変換部２４０は、部分色調整の原理に基づいて所望の部分色調整をし、移動逆変換処理部２５０に送出する。移動逆変換処理部２５０移動処理部２２０にて実施された回転移動の逆変換や平行移動の逆変換を実施して、次段の色変換部４０へＬ^＊ａ^＊ｂ^＊色信号を出力する。
【００８０】
図９は、１次領域内外判定部２１０が取り扱う１次領域を説明する図である。図中、Ｌ^＊，ａ^＊，ｂ^＊各軸にて入力色空間が示されており、円筒が平行移動と回転移動を行なう前の調整対象領域（変換対象領域）Ｐの状態を示す。この円筒をほぼ完全に含むようなＬ^＊，ａ^＊，ｂ^＊各軸に平行になるような、直方体を求めこれを１次領域とする。この直方体は、円筒状の調整対象領域Ｐを含み、できるだけ小さい方が好ましい。Ｌ^＊ａ^＊ｂ^＊色信号が該直方体の内部に入っているか否かを判定することが１次領域内外判定である。このような直方体に対する内外判定は極めて簡単であり処理時間の短縮に効果が大きい。この１次領域内外判定で、外部であると判定した場合は、１次領域内外判定部２１０は、色変換部１０から部分的色調整部２０に入力されたＬ^＊ａ^＊ｂ^＊色信号をそのまま色変換部４０に出力する。
【００８１】
図１０は、部分的色調整パラメータ取得部３０の一構成例を説明する図であって、ユーザインターフェース画面を示すものである。たとえばキーボート、マウスなどのユーザインターフェースからオペレータの入力によりパラメータが取得される。
【００８２】
部分的色調整パラメータ取得部３０は、オペレータからの指示に基づいて、移動対象部分色空間Ｐ１や移動先部分色空間Ｐ２の形状を特定する。たとえば、オペレータは、移動対象部分色空間Ｐ１や移動先部分色空間Ｐ２の形状とこの形状に応じた中心座標とを指定する。これを受けて、部分的色調整パラメータ取得部３０は各領域形状を特定する。部分的色調整部２０は、この領域情報に基づいて変換対象領域Ｐを特定して前述の部分的色調整を実施する。
【００８３】
このような移動対象部分色空間Ｐ１や移動先部分色空間Ｐ２などを特定するためのユーザ指示を受け付けるため、図示するように、表示画面は、移動対象部分色空間Ｐ１および移動先部分空間の形状の指定を受け付けるダイアログボックス３１０、移動対象部分色空間Ｐ１の中心座標と移動先部分空間の中心座標を入力するためのダイアログボックス３２０、移動対象部分色空間Ｐ１および移動先部分空間の形状に依存した部分的色調整に関わるパラメータを入力するためのダイアログボックス３３０、Ｌ^＊ａ^＊ｂ^＊色空間の色票を指定するためのダイアログボックス３４０、色票を表示する色票表示領域３５０、および入力画像を表示する画像表示領域３６０を有する。
【００８４】
部分的色調整に関わるパラメータの１つは、移動対象部分色空間Ｐ１および移動先部分空間の形状である。図中ダイアログボックス３１０により移動対象部分色空間Ｐ１および移動先部分空間の形状を選択する。初期値は球である。
【００８５】
移動対象部分色空間Ｐ１および移動先部分空間の形状に依存した部分的色調整に関わるパラメータは、ダイアログボックス３３０に示す移動対象部分色空間Ｐ１と移動先部分空間の半径などである。図では、球が選ばれたときのダイアログボックスを示しており、ダイアログボックス３１０で楕円面が選択された場合には、それぞれ３方向の半径を入力するようなダイアログボックスに切り替わる。初期値は自動であり、自動が選択されると、球であれば、この後、決定される移動対象部分色空間Ｐ１の中心座標と移動先部分空間の中心座標の距離から自動的に半径が、中心座標間距離の半分になるように決定される。円筒の場合も同様である。
【００８６】
楕円体が選択された場合は、球とみなし、球が選択された場合の自動と同じである。つまり、部分的色調整パラメータ取得部３０は、このダイアログボックス３１０を利用して、移動対象部分色空間Ｐ１や移動先部分色空間Ｐ２の形状が球形の場合にはその球形の半径を、球形以外の場合には、球形に対して半径を指定することに相当する形状の大きさを特定する。
【００８７】
残る部分的色調整に関わるパラメータは、移動対象部分色空間Ｐ１の中心座標と移動先部分空間の中心座標である。図中ダイアログボックス３２０により、直接、Ｌ^＊ａ^＊ｂ^＊色空間の座標値を入力できる。ただし、Ｌ^＊ａ^＊ｂ^＊色空間の座標値は、感覚的に分かりにくいため、図中色票表示領域３５０に予め定められた色票を表示し、オペレータが目視確認してマウスなどの指示部材でクリックすることで座標値を取得するようにしてもよい。
【００８８】
なお、図中ダイアログボックス３２０の移動元座標は移動対象部分色空間Ｐ１の中心座標を指し、移動先座標は移動先部分空間の中心座標を指す。また、図中ダイアログボックス３２０は移動元座標の入力がアクティブになっていることを示している。色票からの入力の場合は、この例では、移動元座標にその色票のＬ^＊ａ^＊ｂ^＊色空間の座標値が表示され、一部の値を変更するなどの操作も可能である。
【００８９】
また、Ｌ^＊ａ^＊ｂ^＊色空間の色票の全て表示するには、スペース的に難しいため、図中ダイアログボックス３４０に示す色立体の一部をマウスでクリックすることにより、その部位を含む、等色相面または等明度面が実際の色票（図中色票表示領域３５０）として表示される。この色票に対応するデータは、Ｌ^＊ａ^＊ｂ^＊色空間のデータであるが、色票を表示する場合は、ディスプレイ表示用にディスプレイＲＧＢに色変換して表示を行なう。この色変換はディスプレイＩＣＣ（Ｉｎｔｅｒｎａｔｉｏｎａｌ　Ｃｏｌｏｒ　Ｃｏｎｓｏｒｔｉｕｍ）プロファイルを用いている。
【００９０】
一般にディスプレイ上の色はそれほど精度よく表示できないので、入力画像をＬ^＊ａ^＊ｂ^＊色空間に色変換した後、色票表示と同一のＩＣＣプロファイルで色変換したものを表示する。すなわち、ディスプレイへのＲＧＢ色空間の表示色とＬ^＊ａ^＊ｂ^＊値の一致精度がそれほどよくなくても、ユーザは、画像と色票が同一条件で比べることができる。
【００９１】
また、表示画像上をクリックしても中心座標を入力することができるようにする。つまり、オペレータは、画像上をクリックしても、色票を選択してクリックしてもよい。また、全てパラメータが決定された場合には、図示はしていないが、プレビューボタンにより、表示画像が部分的調整を施された場合の画像の表示になり、プレビュー前の状態に戻したければ、プレビューキャンセルボタンにより、以前の表示画像に戻るようにする。設定またはプレビュー終了後、図示はしていないが、設定終了ボタンをクリックすることにより設定を終了する。
【００９２】
また、図示はしないが、収斂型部分的色調整に関するユーザインターフェース画面も選択することができる。この場合、上述の部分的色調整に、移動対象部分色空間Ｐ１に対する収斂領域の大きさの比を入力するダイアログボックスが付加されるのみである。大きさの比は“０”以上“１”以下である。
【００９３】
上記構成の画像処理装置１においては、ユーザ指定を受け付けて色調整するようにしていたが、これに限らず、自動調整する形態としてもよい。この場合、オペレータによるユーザインターフェースを介した部分的色調整に関わるパラメータ設定が不要になる。自動調整の事例としては、たとえば、記憶色の好ましい再現が挙げられる。人の肌色、空の青、草の緑などが記憶色といわれ、Ｌ^＊ａ^＊ｂ^＊色信号を移動先部分空間の中心座標に相当する色が分かっているものがある。このような場合は、画像データの色空間上の３次元ヒストグラムなどで画像の色分布をみて、記憶色に近い色があれば、それを移動対象部分色空間Ｐ１の中心座標とし、分布から半径を決定して、好ましい再現に近づけるように部分色調整を行なうことができる。
【００９４】
さらに好適な方法として、特に肌色の場合は、色分布だけではなく、画像中に人物の顔が存在するか否かの顔認識などの方法と組み合わせ、画像中の肌色領域を抽出して、抽出された領域のみで、色分布を見るなどの処理を行ない、部分的色調整を実施すればよい。
【００９５】
また、下地除去などにも有効な手段となる。たとえば、原稿があって、スキャナやデジタルカメラなどの撮像系により画像データを取得した場合、紙の白や、色票など均一な色で再現されているべきものが、すなわち、画像データの画素値が一定値であるべきものが、現実にはある分布（バラツキ）を持ってしまっているケースがある。このような画像データに対しては、下地部分の色情報を一定値にするため、上述の収斂型部分的色調整を適用するのが好ましい。
【００９６】
特に、本来均一であるべき画像データにバラツキが生じているような画像データを圧縮する場合、この収斂型部分的色調整を行なうことにより、非常に圧縮率が上がる場合があるなど、効果は大きい。この収斂型部分的色調整を適用しても、本来の変換対象領域Ｐについては、調整対象領域外との境界部では色飛びや階調逆転などの現象が殆ど生じないのは前述の通りである。
【００９７】
図１１は、上述の部分的色調整方法を利用する、色変換のための色変換定義について説明する図である。ここで、色変換定義は、上記画像処理装置１において色変換係数と表現していたものと同義である。
【００９８】
色変換定義とは、入力色空間から出力色空間への対応を定義したものであり、数学的には関数関係にあるものを指す。実際には、１次元のルックアップテーブル（ＬＵＴ）のテーブル値、多次元のＬＵＴ（ＤＬＵＴ；ｍｕｌｔｉ−Ｄｉｍｅｎｓｉｏｎ　ＬＵＴ）のテーブル値、マトリクスの要素の値であり、それらの組み合わせで実現される。これらの値を総称してプロファイルという。色変換定義の例として、最も一般的なのが、ＩＣＣで制定されたＩＣＣプロファイルである。特に、上述した部分的色調整と組み合わせて有効なのは、ＤＬＵＴの場合である。ＤＬＵＴは、たとえば図１１（Ａ）に示すように、入力色空間をアドレスとした規則正しい多次元（図では３次元）の格子点で構成され、格子点には格子点に対応した出力色空間上の値が記憶される。
【００９９】
格子点に位置する入力値が入ってきた場合は、その格子点の値を出力値とする。一方、格子点間に位置する入力値が入ってきた場合は、近傍格子点を参照して補間を行ない出力値とする。一部の格子点の出力値を変更しても全体に影響を及ぼすことはないためである。
【０１００】
ここで、格子点のデータ値を変更すれば出力の色値が変更される。つまり、このようなルックアップテーブルの特定の格子点データを編集すれば、特定の色についてのみ部分的に色調整することができ。また、たとえば、図１１（Ｂ）に示すように、格子点Ｊ１，Ｊ２，Ｊ３，Ｊ４といった複数の格子点を含む収斂領域を設定し、その領域内の格子点の値を全て同一とすれば、前述の収斂型部分的色調整を実現することもできる。すなわち、図１１（Ｂ）における格子点Ｊ１，Ｊ２，Ｊ３，Ｊ４を中心とする領域内の点を全て同一の色値にすれば、格子点Ｊ１，Ｊ２，Ｊ３，Ｊ４内に対応する入力色値は全て同一の色値に移動させることができ、それ以外の入力色値は、前述の部分的色調整により、調整対象領域外との境界部における階調の連続性を維持し、色逆転を防止するように部分的色調整を行なうことができる。
【０１０１】
なお、図１１（Ｂ）は２次元ＬＵＴにおける好適な例を示したもので、収斂領域が正方格子を構成する格子点Ｊ１，Ｊ２，Ｊ３，Ｊ４により画定されるものとしているが、その形状は必ずしも正方である必要はなく、長方形であってもよい。また収斂領域を画定するための格子点の数は必ずしも“４”に限定されるものではなく、少なくとも“２”以上であればよく、たとえば“３”とすれば三角形で囲まれた領域が収斂領域となる。また“２”とすれば、ある一方向における一定範囲内が収斂領域となる。
【０１０２】
また、３次元ＬＵＴの場合、正方格子状の８つの格子点で画定される範囲を収斂領域とするのがよい。勿論、この場合にも、収斂領域を画定するための格子点の数は必ずしも“８”に限定されるものではなく、少なくとも“２”以上であればよく、たとえば“３”として３つの格子点を３次元状に配すれば、三角推で囲まれた領域が収斂領域となる。
【０１０３】
図１２は、上述の部分的色調整方法を利用することで色変換定義の編集を実施するプロファイル編集装置の一実施形態を示すブロック図である。プロファイル編集装置２は、色変換のための色変換定義に対して、上述の部分的色調整を利用することで、予め用意されている色変換定義を編集する。
【０１０４】
プロファイル編集装置２は、少なくともＤＬＵＴを含むプロファイルに対して編集を行なう。つまり、上述の部分的色調整を利用して色変換係数を求め、この求めた色変換係数を、予め用意されている色変換定義の係数と置き換えることにより、色変換定義の一例である入力プロファイルを編集する。たとえば、予めプロファイル生成装置で作成されたプロファイルに上述の部分的色調整を施して、プロファイルの一部、すなわち、ＤＬＵＴの一部の格子点に記憶されている出力値に変更を加える。本実施形態では、ＤＬＵＴの出力値がＬ^＊ａ^＊ｂ^＊色空間のデータである例にて説明する。
【０１０５】
図１２に示すように、プロファイル編集装置２は、プロファイル生成装置にて生成された入力プロファイルを取り込む入力プロファイル取得部６０と、変換対象領域Ｐ内の各色点について、上述のようにして色座標を移動することで部分的色調整を実施する色座標移動部の一例であるプロファイル編集部７０と、このプロファイル編集部７０における移動パラメータを設定する移動パラメータ設定部の一例である部分的色調整パラメータ取得部８０と、プロファイル編集部７０にて編集された出力プロファイルをプロファイル生成装置に返す出力プロファイル送出部９０とを備える。プロファイル編集部７０は、部分的色調整部２０と同様に、係数取得部７２を有している。
【０１０６】
プロファイル編集部７０および部分的色調整パラメータ取得部８０により、本発明に係る色調整装置４００の一実施形態が構成される。
【０１０７】
この構成において、プロファイル編集装置２は、入力プロファイル取得部６０にて取得した入力プロファイルに変更を加える前に、部分的色調整パラメータ取得部８０により、部分的色調整パラメータを取得しておく。部分的色調整パラメータ取得部８０は、取得した部分的色調整パラメータをプロファイル編集部７０にセットする。プロファイル編集部７０は、このセットされた部分的色調整パラメータに基づいて入力プロファイル取得部６０により取得された入力プロファイルを編集する。この編集後のプロファイルは出力プロファイルとして、出力プロファイル送出部９０を介してプロファイル生成装置に送出される。
【０１０８】
ＤＬＵＴは、色票画像データと等価と考えても差し支えなく、そのように考えると、基本的には、画像処理装置１で説明したと同様の部分色調整を実施すればよくなる。ただし、色空間中、格子点は間欠的にしか存在しないので、移動対象部分色空間Ｐ１の中心座標は格子点に記憶されているＬ^＊ａ^＊ｂ^＊値とする方が、効果が期待できる。勿論、格子点間の値であってもかまわないが、本実施形態では、格子点を指定できるようにする。
【０１０９】
図１３は、部分的色調整パラメータ取得部８０の一構成例を説明する図であって、ユーザインターフェース画面を示すものである。たとえばキーボート、マウスなどのユーザインターフェースからオペレータの入力によりパラメータが取得される。
【０１１０】
図示するように、この部分的色調整パラメータ取得部８０は、画像処理装置１における部分的色調整パラメータ取得部３０とほぼ同様のユーザインターフェース画面を生成する。図示するように、移動対象部分色空間Ｐ１および移動先部分空間の形状の指定を受け付けるダイアログボックス８１０、移動対象部分色空間Ｐ１の中心座標と移動先部分空間の中心座標を入力するためのダイアログボックス８２０、移動対象部分色空間Ｐ１および移動先部分空間の形状に依存した部分的色調整に関わるパラメータを入力するためのダイアログボックス８３０、Ｌ^＊ａ^＊ｂ^＊色空間の色票を指定するためのダイアログボックス８４０、色票を表示する色票表示領域８５０を有する。これらは、部分的色調整パラメータ取得部３０が生成する表示画面と同じである。
【０１１１】
また、表示画面は、入力プロファイルをａ^＊−ｂ^＊平面、Ｌ^＊−ａ^＊平面、Ｌ^＊−ｂ^＊平面の３平面で表示する表示するプロファイル表示領域３６０と、ＤＬＵＴを対象として色票を指定するためのダイアログボックス８７０とを有する。この２点が、上記部分的色調整パラメータ取得部３０が生成する表示画面と異なるところである。
【０１１２】
表示するための色票を選択する図中ダイアログボックス８７０は、ＤＬＵＴが対象であるため、読み込まれたプロファイル中のＤＬＵＴを表示する。したがって、ユーザは、ダイアログボックス８７０において、ａ^＊−ｂ^＊平面、Ｌ^＊−ａ^＊平面、Ｌ^＊−ｂ^＊平面の３平面の中からいずれかを選択する。また色票表示領域８５０に表示される色票は、ＤＬＵＴの格子点を色票化したものである。なお、ダイアログボックス８４０とダイアログボックス８７０とは同時には選択できないようにする。ダイアログボックス８４０も、格子点間を中心座標にしてする場合に使用でき、移動対象部分色空間Ｐ１の中心座標と移動先部分空間の中心座標の指定に使用できる。
【０１１３】
さらに、プロファイル編集装置２に入力されるものがプロファイルであるため、図示した画面例においては、画像処理装置１における画像表示領域３６０であった部位にプロファイル表示領域８６０を設けている。このプロファイル表示領域８６０には、選択された色票を交点とするような、ａ^＊−ｂ^＊平面、Ｌ^＊−ａ^＊平面、Ｌ^＊−ｂ^＊平面の３平面で、格子点間を補間して、連続調でプロファイルを表示する。この表示により、ユーザは、プレビューを行なった場合に、極端な編集を行なって不自然なプロファイルにならないかどうかを確認することができる。
【０１１４】
また、図示はしないが、収斂型部分的色調整に関するユーザインターフェース画面も選択することができる。この場合、上述の部分的色調整に、移動対象部分色空間Ｐ１に対する収斂領域の大きさの比を入力するダイアログボックスが付加されるのみである。大きさの比は“０”以上“１”以下である。この点についても、画像処理装置１における部分的色調整パラメータ取得部３０と同じである。
【０１１５】
また、上述の収斂型部分的色調整を色変換定義に適用することもできる。複数のＤＬＵＴ格子点を収斂領域に指定することにより、概ね収斂領域に属するＤＬＵＴ格子点では、一定の色とすることができる。たとえば、画像処理装置１における収斂型部分的色調整で示したように、下地除去的な効果を色変換定義に付加することもできる。また、色変換定義をＲＧＢ色空間からＬ^＊ａ^＊ｂ^＊色空間へのＤＬＵＴを用いた色変換として、色変換定義の逆変換を色変換定義、すなわちＬ^＊ａ^＊ｂ^＊色空間からＲＧＢ色空間へのＤＬＵＴを用いた色変換とすることもできる。
【０１１６】
この場合、入力ＲＧＢを色変換定義で一旦Ｌ^＊ａ^＊ｂ^＊色空間にした後、別の色変換定義で出力ＲＧＢを生成する。概ね入力ＲＧＢと出力ＲＧＢは同じであることが期待される。ところが、入力ＲＧＢでの、Ｒ，Ｇ，Ｂ単色が出力ＲＧＢで単色になっているかというと、必ずしもそのようのようにならならい場合が多い。なぜならば、出力ＲＧＢ用の色変換定義のＬ^＊ａ^＊ｂ^＊格子点は入力ＲＧＢ用の色変換定義と無関係に作成されるためである。入力ＲＧＢが単色のとき出力ＲＧＢも単色であるようにしたい場合には、出力ＲＧＢ用の色変換定義の適切な格子点に対して収斂型部分的色調整調整を行ない、出力ＲＧＢ用の色変換定義の出力値を単色にすれば効果的である。
【０１１７】
図１４は、上述のプロファイル編集装置２により編集された出力プロファイルを利用して色変換する画像処理システムの一実施形態を示すブロック図である。図示するように、画像処理システム９は、画像処理装置１と、プロファイル編集装置２と、プロファイル生成装置５００とにより構成されている。プロファイル編集装置２は、上記実施形態で説明したものと同様のものである。
【０１１８】
上述した画像処理装置１においては、入力画像の個々の色座標値を変換対象の色として変換後の色座標値を１つずつ求めることで、入力画像中の特定の色を部分的に他の色に色変換することも可能であるが、このような逐次処理は時間がかかり、実用的でない。これに対して、プロファイル編集装置２により予め色域変換のための係数（色変換係数）で構成された入力プロファイルを編集しておき、この編集後の出力プロファイルを用いて入力画像を色域変換するようにしたのが、この画像処理システム９である。
【０１１９】
プロファイル編集装置２は、上述した部分的色調整処理を利用して、プロファイル生成装置５００にて生成されている入力プロファイル（具体的にはルックアップテーブル）上の色変換係数を編集するのは上述の通りである。プロファイル編集装置２は、この編集した色域変換係数から構成された出力プロファイルをプロファイル生成装置５００に返す。プロファイル生成装置５００は、プロファイル編集装置２から受け取った出力プロファイルを画像処理装置１に設けられた記憶媒体２８に書き込んでおく。
【０１２０】
すなわち、この記憶媒体２８には、上述した部分的色調整処理を利用して編集された色変換のための色変換係数が格納される。このとき、記憶媒体２８には、入力画像の調整対象色域内の入力色座標値と出力色座標値との関係を、入力画像を色域変換するために用いられる多次元変換テーブルに格納される格子点データとして格納する。画像処理装置１は、この格子点データと補間演算とによって入力画像を色域変換する。
【０１２１】
図１４は、入力画像信号ＳｉｎがＲＧＢデータであり、変換後のデータをカラー画像出力装置の一例であるカラーディスプレイ７に入力する例を示したものである。ＲＧＢデータの入力画像信号Ｓｉｎは、画像入力部３を介して色変換部１０に入力される。そして、色変換部１０によってＬ^＊ａ^＊ｂ^＊データに変換され、その変換後のＬ^＊ａ^＊ｂ^＊データが、部分的色調整部２０に供給される。
【０１２２】
図示するように、上記実施形態の部分的色調整部２０および色変換部４０は、３次元テーブル２５、補間演算部２６、および１次元テーブル２７ｒ，２７ｇ，２７ｂによって構成され、３次元テーブル２５には、上述したプロファイル編集装置２によって編集されたＲＧＢデータの格子点データが、あらかじめ格納される。３次元テーブル２５、および１次元テーブル２７ｒ，２７ｇ，２７ｂによって記憶媒体２８が構成される。
【０１２３】
そして、色変換部１０からのＬ^＊ａ^＊ｂ^＊データの上位ビットによって３次元テーブル２５が索引されて、３次元テーブル２５から格子点データが読み出され、その読み出された格子点データが、補間演算部２６において、色変換部１０からのＬ^＊ａ^＊ｂ^＊データの下位ビットによって補間演算されて、３次元テーブル２５から色域変換後のＲＧＢデータＲｉ，Ｃｉ，Ｂｉが得られる。
【０１２４】
補間方法としては、たとえば単位立方体を６つの３角錐に分割して補間演算する方法、単位立方体を２つの３角柱に分割して補間演算する方法、あるいは単位立方体にそのまま補間する方法など、公知の補間処理を適用すればよい。
【０１２５】
このように格子点データの補間演算によって色域変換後の色を求めるため、格子点データの生成や編集に当たっては、格子点として入力画像の色域外に位置する点も含ませる。そのため、色域変換後の色として３次元テーブル２５から得られるＲＧＢデータＲｉ，Ｃｉ，Ｂｉにはディスプレイ再現域外の色も含まれる。
【０１２６】
そこで、３次元テーブル２５からのＲＧＢデータＲｉ，Ｇｉ，Ｂｉは、１次元テーブル２７ｒ，２７ｇ，２７ｂによって、再現先デバイスであるディスプレイ色域内の色信号はできるだけ補正せずに、且つディスプレイ色域外の色信号は彩度の逆転ができるだけ発生しないように色域マッピング処理をし、この色域マッピング処理後のＲＧＢデータＲｏ，Ｇｏ，Ｂｏがディスプレイ７に出力される。
【０１２７】
なお、上記の実施形態は、部分的色調整部２０やプロファイル編集部７０の機能部分をハードウェアにて構成するものとして説明したが、これに限らず、マイコンなどのＣＰＵ（中央演算処理装置）やパソコンなどの、いわゆる電子計算装置を利用し、ソフトウェアにて、上記の処理機能を実現することもできる。
【０１２８】
この場合、マイコンやパソコンなどの電子計算装置は、前述の部分的色調整パラメータ取得部３０やプロファイル編集部７０などの各機能部分をソフトウェアとして備える。すなわち、前述の部分的色調整パラメータ取得部３０やプロファイル編集部７０などの各機能部分を実現するソフトウェアのプログラムコードを記録した記憶媒体（たとえば図示しないＲＡＭなど）から、装置のコンピュータ（またはＣＰＵやＭＰＵ）がプログラムコードを読出し実行することによって、前述の実施形態で述べた効果が達成される。この場合、記憶媒体から読み出されたプログラムコード自体が前述の実施形態の機能を実現することになる。なお、プログラムは、記憶媒体を介して提供されるものに限らず、有線あるいは無線による通信手段を介して配信されるプログラムデータをダウンロードしたものであってもよい。
【０１２９】
また、コンピュータが読み出したプログラムコードを実行することで各機能が実現されるだけでなく、そのプログラムコードの指示に基づき、コンピュータ上で稼働しているＯＳ（オペレーティングシステム）などが実際の処理の一部または全部を行ない、その処理によって各機能が実現される場合であってもよい。さらに、記憶媒体から読み出されたプログラムコードが、コンピュータに挿入された機能拡張カードやコンピュータに接続された機能拡張ユニットに備わるメモリに書き込まれた後、そのプログラムコードの指示に基づき、機能拡張カードや機能拡張ユニットに備わるＣＰＵなどが実際の処理の一部または全部を行ない、その処理によって前述の実施形態の各機能が実現される場合であってもよい。
【０１３０】
以上、本発明を実施形態を用いて説明したが、本発明の技術的範囲は上記実施形態に記載の範囲には限定されない。発明の要旨を逸脱しない範囲で上記実施形態に多様な変更または改良を加えることができ、そのような変更または改良を加えた形態も本発明の技術的範囲に含まれる。
【０１３１】
また、上記の実施形態は、クレーム（請求項）にかかる発明を限定するものではなく、また実施形態の中で説明されている特徴の組合せの全てが発明の解決手段に必須であるとは限らない。前述した実施形態には種々の段階の発明が含まれており、開示される複数の構成要件における適宜の組み合わせにより種々の発明を抽出できる。実施形態に示される全構成要件から幾つかの構成要件が削除されても、効果が得られる限りにおいて、この幾つかの構成要件が削除された構成が発明として抽出され得る。
【０１３２】
【発明の効果】
以上のように、本発明によれば、調整対象領域の範囲内では、階調の連続性を維持し、かつ、色の逆転を発生させることなく、調整対象領域内の色を入力色空間と同一色空間である出力色空間上の別の色に変換するための係数を求めるようにした。つまり、調整対象の色空間中で、特定領域の色座標をある領域に移動するに際して、移動しない領域との境界部において階調性や色の連続性を損なうことなく、すなわち疑似輪郭や階調逆転などの画質欠陥が生じることなく、部分的色調整を行なうことができる。
【０１３３】
よって、移動対象部分色空間と移動先部分色空間とを結ぶ領域として画定される変換対象領域内を調整対象色空間として取り扱うことで、従来の手法で制約事項となっていた内包関係の制約を取り外すことができる。そしてこれにより、たとえば、移動したい色の中心と半径や移動先の中心と半径は独立に与えることができ、色調整の自由度が大きくなる。また、自由度の高い選択的色調整機能が実現できる。
【図面の簡単な説明】
【図１】本発明に係る色調整方法の一実施形態において処理対象とする移動対象部分色空間、移動先部分色空間、および調整対象色空間の関係を説明する図である。
【図２】色調整時の重み付けを説明する図である。
【図３】変換対象領域の形状を円筒形とする場合の色調整について説明する図である。
【図４】調整対象領域がカプセル形状の場合における色調整について説明するものである。
【図５】移動対象部分色空間と移動先部分色空間が相似関係にある場合における色調整について説明する図である。
【図６】収斂型部分的色調整について説明する図である。
【図７】部分的色調整方法を実施する画像処理装置の一実施形態を示すブロック図である。
【図８】画像処理装置における部分的色調整部の詳細構成例を示すブロック図である。
【図９】１次領域内外判定部が取り扱う１次領域を説明する図である。
【図１０】部分的色調整部における部分的色調整パラメータ取得部が生成するユーザインターフェース画面を示す図である。
【図１１】部分的色調整方法を利用する、色変換のための色変換定義について説明する図である。
【図１２】部分的色調整方法を利用することで色変換定義を実施するプロファイル編集装置の一実施形態を示すブロック図である。
【図１３】プロファイル編集装置における部分的色調整パラメータ取得部が生成するユーザインターフェース画面を示す図である。
【図１４】プロファイル編集装置により編集された出力プロファイルを利用して色変換する画像処理システムの一実施形態を示すブロック図である。
【符号の説明】
１…画像処理装置、２…プロファイル編集装置、３…画像入力部、５…画像データ出力部、１０，４０…色変換部、２０…部分的色調整部、２２，７２…係数取得部、３０…部分的色調整パラメータ取得部、６０…入力プロファイル取得部、７０…プロファイル編集部、８０…部分的色調整パラメータ取得部、９０…出力プロファイル送出部、２１０…１次領域内外判定部、２２０…移動処理部、２３０…２次領域内外判定部、２４０…部分色調整変換部、２５０…移動逆変換処理部、３１０，３２０，３３０，３４０…ダイアログボックス、３５０…色票表示領域、３６０…画像表示領域、８１０，８２０，８３０，８４０，８７０…ダイアログボックス、８５０…色票表示領域、８６０…プロファイル表示領域、Ｐ…変換対象領域、Ｐ０…調整対象色空間、Ｐ１…移動対象部分色空間、Ｐ２…移動先部分色空間[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color adjustment method, a color adjustment device, a color conversion definition editing device, an image processing device, a program, and a computer-readable storage medium storing the program. More specifically, the present invention relates to a color image color adjustment function and a color image color conversion coefficient editing function in a color image processing apparatus or a color image color conversion coefficient generation apparatus. More specifically, a device such as a digital color copier, a printer, a printer driver, a printer controller, a color FAX, or a color display, which includes color adjustment as a part of its functions, and a profiler that generates a color conversion coefficient (profile). The present invention relates to a technology for converting a color in a certain color space coordinate system into another color in the same color space in a color conversion generation device or a device for editing or adjusting a profile.
[0002]
[Prior art]
One of the functions for adjusting a digital color image is a color adjustment function. If the color adjustment function has low relevance to the perception of human colors such as hue, saturation, and lightness, it is often difficult to perform the desired conversion. Conversely, computer graphics (CG) designers that directly handle RGB, and printing-related designers that mainly handle CMYK directly, are usually used to editing RGB and CMYK. In some cases, you can edit as intended. As described above, the color space for color adjustment varies widely depending on the target field.
[0003]
The color adjustment can be broadly classified into a full-range color adjustment that affects the entire color space to which the digital color image belongs, and a partial color adjustment that affects only the partial color space. Specific examples of the entire gamut color adjustment include contrast enhancement, saturation enhancement, and color balance adjustment. Specific examples of the partial color adjustment include an example of adjusting only the skin color.
[0004]
As a technique relating to the gamut color adjustment, for example, Japanese Patent Application Laid-Open No. 64-16658 discloses that an RGB color signal from a scanner is converted into an HLS color signal, and a hue (H), a lightness (L), and a saturation (S) are set for each color. There is disclosed a method of performing color adjustment and color correction in a form that matches human perception by performing conversion using an independent look-up table, and inversely converting the converted HLS color signal into an RGB color signal.
[0005]
However, this method adjusts the overall color or corrects the color.For example, it reproduces only the colors that a person has as an image, such as skin color, so-called memorized colors into desirable colors, and so on. It is difficult to adjust only local colors that often appear in human needs.
[0006]
On the other hand, as a technique relating to partial color adjustment, for example, Japanese Patent Application Laid-Open No. 2-96477 discloses that a color conversion unit is constituted by a color developing unit, a memory color adjusting unit, and a reverse color developing unit, and a color conversion unit is provided. The RGB color signals are converted into color signals suitable for human senses such as hue, saturation, and lightness, and the target area designation table is used to store only target areas of memory colors such as flesh colors with non-target areas. Discloses a method of performing color adjustment independently of masking by performing conversion so as not to cause discontinuity, and inversely converting the converted color signal into an RGB color signal.
[0007]
The method disclosed in Japanese Patent Application Laid-Open No. 2-96477 is to perform smooth local color adjustment by multiplying a movement amount by using a function of a distance from a movement center (center of gravity) as a weight. (Hue Hue, Saturation Saturation) is handled independently, so there is a disadvantage that it cannot be applied to a color space in which lightness is not independent, such as an RGB space. In other words, the moving distance and the affected range are dependent upon adding a condition that does not cause gradation inversion, and the local color adjustment amount is determined by the center of gravity, the moving vector, and the weight function (distance from the center of gravity and the applicable range). Therefore, it is difficult to apply the method to systems other than lightness / chromaticity separation systems. Further, in order to adjust a plurality of colors, it is necessary to take a method such as increasing the number of target area designation tables, and there is a disadvantage that the load on hardware is increased.
[0008]
Japanese Patent No. 3009934 (Japanese Patent Laid-Open No. 4-321182) discloses a representative image representing a color of an adjustment target area based on image data representing a color of each pixel included in the adjustment target area extracted from a color image. Determine the color, according to the input of the target color as the target of the adjusted color of the adjustment target area, obtain a basic vector indicating the movement in the color space from the representative color to the target color, the direction indicated by the basic vector and A technique is disclosed in which image data included in an adjustment target area is moved in a color space according to a distance. Specifically, a representative color representing the color of the adjustment target area is determined, a movement vector is obtained from the adjusted target color, a distance weight is obtained from the distance between the color of each pixel and the target color, and a movement vector is obtained. Is multiplied by the weighting factor to obtain the movement amount.
[0009]
Japanese Unexamined Patent Publication No. Hei 9-214792 discloses a method of specifying a color coordinate before and after conversion and specifying a range such as a sphere or an ellipsoid including the color coordinates so that the color is not discontinuous outside the partial range. A method for performing the adjustment is disclosed. This method solves the problem of separately treating lightness (independently calculating the distance with lightness and chromaticity) in the method described in JP-A-2-96477. , L ^* a ^* b ^* A technique for solving the problem by determining the weight of the movement based on the Euclidean distance from the center of gravity in a color space such as a color space is disclosed.
[0010]
According to this method, an arbitrary color in an arbitrary color space coordinate system can be converted into another color in the same color space so as not to cause a discontinuity with a non-target color, A plurality of colors can be converted into different colors, and in that case, the weight coefficient function is not limited to one when the weight coefficient function is switched as well as when the weight coefficient function is fixed for each color. Since it can be realized by a dimensional lookup table, there is an advantage that no load is imposed on hardware.
[0011]
However, although this method has a higher degree of freedom than the method described in Japanese Patent Application Laid-Open No. 2-96477, the moving distance and the range affected by the method are dependent on the addition of a condition that does not cause gradation inversion. There is no.
[0012]
The features common to the above-mentioned JP-A-2-96477, JP-A-3009934 (JP-A-4-321182), and JP-A-9-214792 are that the color before adjustment is changed from the color before adjustment in the adjustment target area. And the conversion is performed so as not to be discontinuous at the boundary between the adjustment target area and the outside of the adjustment target area.
[0013]
[Problems to be solved by the invention]
By the way, the above-described prior art focuses only on the continuity of color reproduction between the adjustment target area and the outside of the adjustment target area when performing partial color adjustment. Not considered. Therefore, when partial color adjustment is performed by applying the conventional technique, an unnatural (perceived by human eyes) image reproduction occurs due to, for example, discontinuity (reversal or rapid change) of gradation. More specifically, for example, considering that the color coordinates before adjustment to be adjusted in the color coordinate space are adjusted to the color coordinates after adjustment, a color adjustment area including the color coordinates before adjustment and the color coordinates after adjustment is considered. Otherwise, a problem such as a grayscale inversion occurs.
[0014]
Further, in the above-described related art, there is no freedom to arbitrarily specify the color coordinates before adjustment, the color coordinates after adjustment, and the adjustment target area, and the minimum adjustment target area is determined by the color coordinates before adjustment and the color coordinates after adjustment. It can be said that. Qualitatively, if the distance between the pre-adjustment color coordinates and the post-adjustment color coordinates increases, there is a restriction that the adjustment target area must be widened.
[0015]
The present invention has been made in view of the above circumstances, and is not limited by an adjustment target area, and can perform color adjustment that can maintain continuity of gradation to be adjusted and prevent color inversion. It is an object of the present invention to provide a method and an apparatus, or a color conversion definition editing apparatus and an image processing apparatus using the color adjustment method.
[0016]
Another object of the present invention is to provide a program suitable for implementing the color adjustment method and apparatus by software using an electronic computer, and a computer-readable storage medium storing the program.
[0017]
[Means for Solving the Problems]
That is, the color adjustment method according to the present invention is a color adjustment method for acquiring a coefficient for performing color conversion from an input color space to an output color space for a predetermined adjustment target area in a color space to which a color image belongs, Within the range of the adjustment target area, the colors in the adjustment target area are stored in the output color space, which is the same color space as the input color space, while maintaining the continuity of gradation and without causing color inversion. A coefficient for converting the color of the color is determined.
[0018]
A color adjustment device according to the present invention is a device that performs the color adjustment method according to the present invention, and maintains color continuity and generates color inversion within a range of an adjustment target area. And a coefficient obtaining unit for obtaining a coefficient for converting a color in the adjustment target area into another color in the output color space that is the same color space as the input color space.
[0019]
The color conversion definition editing device according to the present invention includes the color adjustment device according to the present invention, and replaces the coefficient acquired by the coefficient acquisition unit of the color adjustment device with a coefficient of a color conversion definition prepared in advance. A coefficient editing unit for editing the color conversion definition is provided.
[0020]
A first image processing apparatus according to the present invention includes a color adjustment apparatus according to the present invention, and an adjustment target area extracted from an input color image based on a coefficient acquired by a coefficient acquisition unit of the color adjustment apparatus. And a partial color adjustment unit that performs color conversion by moving pixel data representing the color of each pixel included in the color space in the color space.
[0021]
A second image processing device according to the present invention includes a storage unit that stores a color conversion definition edited by the color conversion definition editing device according to the present invention, and a color conversion definition stored in the storage unit. The image processing apparatus further includes a partial color adjustment unit that performs color conversion by converting pixel data representing the color of each pixel included in the adjustment target area extracted from the input color image.
[0022]
The invention described in the dependent claims defines a further advantageous specific example of the color adjustment method, the color adjustment device, the image processing device, or the color conversion definition editing device according to the present invention. Furthermore, the program according to the present invention is suitable for implementing the color adjustment method and the color adjustment device according to the present invention by software using an electronic computer (computer). The program may be provided by being stored in a computer-readable storage medium, or may be distributed via a wired or wireless communication unit.
[0023]
[Action]
In the above configuration, within the range of the adjustment target area, the continuity of gradation is maintained, and the color in the adjustment target area is output in the same color space as the input color space without causing color inversion. Find coefficients for conversion to another color in the color space. In other words, when the color coordinates of a specific area are moved to a certain area in the color space to be adjusted, the gradation and color continuity are not impaired at the boundary with the non-moving area. A color conversion coefficient that does not cause image quality defects such as inversion is obtained. Also, partial color adjustment is performed by using this method, and the color conversion definition is edited.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the concept of an embodiment of the color adjustment method according to the present invention will be described.
[0025]
The color space is a device-dependent color space depending on devices such as an RGB color space, a YCC (Y, c1, C2) color space, a CMYK color space, and a color space expressed by four or more colors, or a CIE (Commission International de I). XYZ color space defined by 'Eclairage), L ^* a ^* b ^* Color space, L ^* u ^* v ^* There are various color spaces, such as a color space, and a device-independent color space that does not depend on devices, such as an sRGB (standard RGB) color space and an sYCC (standard YCC) color space. In many cases, the color space is expressed in three dimensions, and is expressed in four or more dimensions in a color space depending on some devices such as CMYK.
[0026]
Partial color adjustment is handled geometrically, and is not restricted by the dimensions or the type of color space. Here, an example of a Euclidean space generally expressed in three dimensions (X, Y, Z) will be described. In addition, the extension to a dimension larger than three dimensions is also possible. Of course, any of the above-described various device-dependent color spaces and the above-described various device-independent color spaces may be handled as signals to be subjected to color adjustment.
[0027]
FIG. 1 is a diagram illustrating a relationship among a target partial color space P1, a destination partial color space P2, and an adjustment target color space P0 to be processed in an embodiment of the color adjustment method according to the present invention. A closed area Q0 (movement target partial color space P1) corresponding to the movement target partial color space P1 centered on coordinates A (X0, Y0, Z0) is moved to a destination area centered on coordinates B (X1, Y1, Z1). Consider partial color adjustment to a closed area Q1 (destination partial color space P2) corresponding to the color space P2. Here, the center of the moving target partial color space P1 is a color point of a representative color representing the color of the moving target partial color space P1, and the center of the moving destination partial color space P2 is the center of the moving destination partial color space P2. This is the color point of the target color that is the target of the color after the conversion process representing the color.
[0028]
The center, which is the representative color of the moving target partial color space P1 or the target color of the moving destination partial color space P2, may be appropriately determined according to the region shape. For example, in the case of a sphere, the center may be set as the center of the region, and in the case of a cube or a rectangular solid, the center of gravity may be set as the center. In other words, it is preferable to set a substantially balanced color point according to the region shape as the region center. Of course, it is only necessary to represent the color of each area, and it is not always necessary to set the center or the center of gravity. Hereinafter, for the sake of simplicity, as shown in FIG. 1, the radius r1 of the closed region Q0 and the radius r2 of the closed region Q1 are both spheres having a radius r (r1 = r2 = r) and are different regions on the color coordinates. A description will be given in the case where it exists. The figure shows only a hemispherical portion.
[0029]
Since the closed areas Q0 and Q1 exist in different areas on the color coordinates, the coordinates A and the coordinates B are not the same. The conversion target area P, that is, the target area of the partial color adjustment includes a movement target partial color space P1 including a color to be converted and a movement destination partial color space P2 including a color of a corresponding color conversion coefficient. As described above, it is more preferable that the shape is included so as to be inscribed. In the illustrated example, the cylinder is defined by a cylinder (the length of the cylinder is equal to the length of the line segment AB) Q3, the spheres Q1, and Q2, which are parallel to the straight line connecting the coordinates A and the coordinates B and are in contact with the spheres Q1 and Q2. In FIG. 1, the maximum range of the inscribed region is a region surrounded by a substantially left half of the sphere Q1, a cylinder Q3, and a substantially right half of the sphere Q2. It is shaped like a capsule of medicine.
[0030]
The shapes of the movement target partial color space P1 and the movement destination partial color space P2 are not limited to the spherical shapes as illustrated, but may be, for example, elliptical surfaces, cylindrical shapes, elliptical cylindrical shapes, rectangular parallelepiped shapes, and at least It may be a closed three-dimensional shape other than the torus shape. Also in these cases, it is preferable that the conversion target region P, that is, the target region for the partial color adjustment, has a shape that includes the moving target partial color space P1 and the moving destination partial color space P2 in an inscribed manner.
[0031]
First, in order to simplify the calculation, as shown in FIG. 1A, in the three-dimensional space (X, Y, Z), the closed area Q0, Q1 is translated while maintaining the relative positional relationship. Thereafter, as shown in FIG. 1B, the closed regions Q0 and Q1 are rotationally moved such that a straight line connecting the coordinates A and the coordinates B overlaps the X axis while maintaining the relative positional relationship. As described above, when the parallel movement and the rotational movement are performed, the result is as shown in FIG. The three-dimensional shape corresponding to the conversion target area P shown in FIG. 1C is called a capsule body. In the color adjustment of the present embodiment, partial color adjustment is performed on the capsule body corresponding to the conversion target area P. Hereinafter, for convenience, a coordinate system in which a straight line connecting the coordinates A and the coordinates B is set as the X axis is referred to as an X'Y'Z 'space.
[0032]
The rotational movement is to rotate the X'Y'Z 'space so that the coordinate axes coincide with the XYZ space. Note that if the coordinate A is originally the origin, no parallel movement is necessary, and if the straight line connecting the coordinate A and the coordinate B is parallel to the X axis, no rotational movement is necessary. Further, when the conversion target area P is a rotator whose center line is a straight line connecting the coordinates A and the coordinates B as in this example, the Y ′ axis and the Z ′ axis are not uniquely determined. In this case, an appropriate constraint condition may be provided, such as determining that an axis included in a plane including the straight line connecting the coordinates A and the coordinates B and the X axis and orthogonal to the X axis is the Y 'axis.
[0033]
Further, when the conversion target area orthogonal to the X ′ axis has directionality like an ellipse, it is convenient to set the major axis and the minor axis to the Y ′ and Z ′ axes. In the case of a three-dimensional space, the rotational movement can be realized by a matrix operation of a 3 × 3 matrix. For example, the rotational movement is described in a textbook of elementary geometry such as “Shokabo, basic mathematics selection 4, three-dimensional analysis geometry”. Method may be used. Either of the rotational movement and the parallel movement may be processed first.
[0034]
As described above, by performing the parallel movement and the rotation movement, the calculation of the movement of the coordinates in the conversion target area P (the capsule body in the example in the figure) accompanying the actual partial color adjustment can be extremely simplified. In addition, after performing these movements, it is necessary to return to the original coordinate system.However, since the parallel movement and the rotation movement are performed, it is necessary to return in the order of the inverse transformation of the rotation movement and the inverse transformation of the parallel movement. Good.
[0035]
FIG. 2 is a diagram illustrating weighting at the time of color adjustment. Here, FIG. 2A illustrates two-dimensional display of the capsule body shown in FIG. 1C and movement of color coordinates.
[0036]
In the color adjustment, the color coordinates may be moved on the coordinate space. For example, as shown in FIG. 2A, the capsule body shown in FIG. Then, the point A is moved so as to overlap the point B, and the surface of the capsule body corresponding to the boundary of the moving area is hardly moved, preferably, is not moved at all (the moving amount is “0”). Further, the closer to the surface of the capsule body corresponding to the boundary of the movement area, the smaller the movement amount. Further, since it can be expressed as a movement from point A to point B, it can be described as a vector, which is called a movement vector. The weight for the movement vector AB is as shown in FIG. 2B when the movement target area is the simplest cylinder. Next, in order to simplify the mathematical description, the case where the shape of the conversion target area P is cylindrical will be described.
[0037]
FIG. 3 is a diagram illustrating color adjustment when the shape of the conversion target area P is cylindrical. As shown in FIG. 3A, it is assumed that points C and D are defined as adjustment ranges. First, consider a movement vector on the X axis.
[0038]
FIG. 3B shows the relationship before and after the movement on the X-axis. The assumption is that the point A is moved to the point B, and the points C and D located at the boundary of the conversion target area P are not moved. If the points C and D have moved, it means that a gradation step or a color step occurs at the boundary between the adjustment target area P and the other areas. In addition, solid arrows indicating movement on the X axis shown in the drawing indicate movements of points A, B, C, and D. Dashed arrows indicate other movements on the X axis. The condition under which the gradation inversion or the color inversion does not occur due to the movement in the conversion target area P is that the solid arrow and the broken arrow do not intersect. That is, on the X axis, a functional relationship that generates such a movement vector may be generated. An example of this function is shown below. Coefficients related to the movement vector correspond to coefficients for color conversion.
[0039]
As shown in FIG. 3C, a point on the section CD is defined as X, and a point A is defined as an origin. The area is divided into two areas at point A, which are referred to as section CA and section AD. When X is in the section CA, the movement vector can be determined by Expression (1). Here, CX is the distance between point C and point X, AC is the distance between point A and point C, “↑ AB” is the vector from point A to point B, and “↑ P” is the movement vector at point X. .
(Equation 1)

[0040]
When X is in the section AD, the movement vector can be determined by Expression (2). Where DX is the distance between points D and X, AD is the distance between points A and D, "↑ AB" is the vector from point A to point B, and "、 P" is the movement vector at point X.
(Equation 2)

[0041]
If the position vector of the point X is “と し AX” and the position vector after the movement is “↑ AY”, Expression (3) is obtained.
[Equation 3]

[0042]
The above means that by dividing at the movement target point A, a movement vector or a movement amount that does not cause the gradation inversion is obtained. CX / AC in equation (1) and DX / AD in equation (2) are values that fall from “0” to “1”, and the movement amount at point X is the simplest relationship. (CX / AC) ² Ya (CX / AC) ^1/2 It may be. In addition, if the relationship is not a function, but is a monotonous relationship, for example, a method of storing data in a table format and performing interpolation during that time may be used.
[0043]
Although the above describes the one-dimensional movement rule on the X axis, the point X is actually an arbitrary point in the adjustment target area. Assuming that the coordinate value of the point X is (x, y, z), since the adjustment target area P is a rotating body having the X axis as a rotation axis, (x, 0, 0) changes to (x, y, z). Is R, the radius of the adjustment target area P is r, and the weight β can be calculated as in Expression (4).
(Equation 4)

[0044]
This equation (4) is also expressed, for example, by (1-R / r) ² For example, the same modification as described above on the X axis can be made. Here, the relationship between the weight β and Expression (1) or Expression (2) will be described. Equations (1) and (2) are collectively expressed as equation (5).
(Equation 5)

[0045]
Expression (5) has been described as a relational expression on the X axis, but can be obtained at an arbitrary point X ignoring the y and z elements. At this time, the movement vector of an arbitrary point in the adjustment target area is represented by Expression (6).
(Equation 6)

[0046]
The above is the description of the case of the cylindrical shape. When the end surface of the adjustment target area that is orthogonal to the X axis is a plane, the same concept as a cylinder may be used. Also, it is obvious that AC and AD are similarly obtained when the cross-sectional shape is an ellipse or the like and not a rotating body.
[0047]
FIG. 4 explains color adjustment when the adjustment target area P has a capsule shape. In the illustrated example, AC and AD are illustrated on the XZ plane, and thick solid lines are examples of AC (left side of A) and AD (right side of A).
[0048]
The capsule shape is slightly more complicated than a cylindrical shape, but the same concept as the cylindrical shape can be applied. Also in this case, since the object is a rotating body, the coordinate value of the point X in the area is (x, y, z), and the adjustment target area is the distance from (x, 0, 0) to (x, y, z). Let R be the radius of the adjustment target area P. The AC in equation (1) and the AD in equation (2) may be changed according to R.
[0049]
The above description describes the principle of smooth movement without causing gradation inversion in the adjustment target area even when the movement target partial color space P1 and the movement destination partial color space P2 do not have an inclusive relationship. When partial color adjustment is performed, particularly when a natural image is targeted, it is important that gradation is not reversed and smoothness is important, and the present method matches this.
[0050]
In the above-described example, the case where the movement target partial color space P1 and the movement destination partial color space P2 are in a congruent relationship is described, but a similar relationship may be used.
[0051]
FIG. 5 is a diagram illustrating color adjustment when the movement target partial color space P1 and the movement destination partial color space P2 have a similar relationship. R1 is the radius to the adjustment target area boundary orthogonal to the X axis including A, r2 is the radius to the adjustment target area boundary orthogonal to the X axis through B, and R is the adjustment target area orthogonal to the X axis through the point R0. A radius r3 to the boundary and a distance between the X axis and the point R0 are R3.
[0052]
In the illustrated example, both the movement target partial color space P1 and the movement destination partial color space P2 have a truncated cone shape. In the case of the congruence, r1 = r2, but in the case of the similarity, r1 ≠ r2. For this reason, the difference is that the direction of the movement vector must be changed depending on the point R0, more strictly on R3. The direction of the movement vector is determined as follows.
[0053]
First, R1 and R2 can be determined so that R3 / r3 = R1 / r1 = R2 / r2. If the movement vector determined by the point R0 is "と A'B '", it is appropriate to determine the X axis and "↑ A'B'" so as not to be in a twisted position. A′B ′ ″ can be determined. Regarding the magnitude of the movement vector before multiplication by the coefficients α and β, the distance in the X-axis direction of “↑ A′B ′” may be | AB | regardless of the position of the point R0. The vector is called a basic movement vector. The basic motion vector can be regarded as a function of the point R0, and if the basic motion vector is expressed as “ΔF (x)”, the motion vector “ΔP” can be obtained by Expression (7).
(Equation 7)

[0054]
In this way, even if the movement target partial color space P1 and the movement destination partial color space P2 have a similar relationship, only the direction of the basic movement vector becomes a function of x. There is no difference from the case where the target partial color space P1 and the destination partial color space P2 have the same shape.
[0055]
The above is a description of the case where the adjustment target area is a rotating body. For example, even when the movement target partial color space P1 and the movement destination partial color space P2 are not rotation targets such as ellipsoids, the above rotation is performed. It can be handled like a target congruent or similar shape. Although the details are omitted, if the radius r and the distance R are congruent at the point R0 (x, y, z), they are functions of the elements y and z of the point X, and if they are similar, x , Y, z. In the above description, the basic movement vector and the coefficients α and β are described using the simplest functions, but these are only examples.
[0056]
A determination method other than the above may be used as long as the basic movement vectors do not intersect. As for α and β, the product of the two can be regarded as a coefficient applied to the basic movement vector, and finally, the color coordinates after the movement are determined by Expression (3). From this point of view, α and β are determined or directly correspond to α · β so that the order of the point sequence before movement and the point sequence after movement on a certain basic movement vector do not reverse. A method of determining the coefficient may be used.
[0057]
As described above, if the color adjustment is performed on the conversion target area P by the above method, the color point to be adjusted is moved toward the target in the conversion target area P so as to overlap the color point after the movement. Since the boundary of the moving area hardly moves or does not move at all, almost no phenomena such as color jump and gradation inversion occur at the boundary outside the adjustment target area. That is, partial color adjustment can be performed while maintaining the continuity of the gradation of the image to be color-adjusted and preventing the color inversion.
[0058]
In preferred reproduction, memory color reproduction is important. The above method is extremely effective when performing selective color adjustment for changing only a specific color in a color space. For example, if a specific color area, for example, a skin color can be changed to a certain color (memory color) by analyzing a document, added value can be provided for preferable reproduction. In addition, the above method has an advantage that it can be applied to a case where a color is to be locally moved in a color space, such as correction of a white point (White Point).
[0059]
In the conventional method, for example, a method of selecting a color from a large ellipsoid in a color space to a small ellipsoid existing in a region completely included in the ellipsoid (inclusive) has been proposed. However, there is a problem that a positional relationship that does not have an inclusive relationship cannot be moved, or that if a color tone is forcibly adjusted, a grayscale inversion occurs in principle. On the other hand, according to the above method, for example, only the conversion target area P defined as the area connecting the spherical destination partial color space P1 and the destination destination partial color space P2 is adjusted. By treating it as P0, the constraint of the inclusive relation is removed.
[0060]
For this reason, for example, the center and radius of the color to be moved or the center and radius of the destination are given independently, and the degree of freedom of adjustment is increased. Thus, a selective color adjustment function having a high degree of freedom can be provided. When moving the coordinates of a specific area to a certain area in a color space, a step at a boundary with a non-moving area can be taken into consideration, and image quality defects such as pseudo contours and grayscale inversion after moving hardly occur. As for the shape of the region, an ellipsoid has a higher degree of freedom than a sphere, but it is difficult to arithmetically find a general solution.
[0061]
Next, the principle of partial color adjustment that is effective for removing background from image data will be described. The base in the image data refers to a portion corresponding to paper on which no ink is applied if it is a printed matter, and if the image is not digitally generated such as CG (computer graphics), for example, In this case, when a scene or a scene is obtained through an imaging system, a part that should be a base has a certain degree of variation. In order to distinguish this method from the above-mentioned partial color adjustment, it is referred to as a convergent partial color adjustment.
[0062]
FIG. 6 is a diagram for explaining the convergent partial color adjustment. In FIG. 6A, convergent partial color adjustment means that all points in the area of the small sphere S centering on point A in FIG. Means that partial color adjustment is performed while maintaining continuity. This sphere S is called a convergent region. In the figure, the boundary between the sphere outside the sphere S and the outer side is converted by the above-described partial color adjustment so that color discontinuity and color inversion do not occur at the boundary. As described above. Assuming that the range of the variation of the background is within the sphere S, the background can be all set to a constant value, and the movement in which the colors in the vicinity can maintain continuity is considered. The convergent partial color adjustment is easy to understand when divided into two stages.
[0063]
As shown in FIG. 6B, a small sphere S centered on the point A, the radius of the sphere S is R2, and a radius R1 of a large sphere (movement target partial color space P1) centered on the point A is this large sphere. Assuming that a point included in the sphere to be moved is X, and a distance from A to X is r, if r <R2, X may be unconditionally the coordinate value of point A. In the region of R2 ≦ r ≦ R1, the direction of the step 1 basic movement vector (this is so as to be distinguished from the above-mentioned basic movement vector of the partial color adjustment) is a vector from the point X to the point A, and the length is This is the distance from point X to point A. Assuming that this step 1 basic movement vector is “↑ V1”, the step 1 movement vector “↑ V1” is obtained by equation (8).
(Equation 8)

[0064]
In Equation (8), the weight γ is represented by a simple function. However, the weight X is monotonically and monotonically changed so that the point X is “1” on the surface of the sphere S and “0” on the surface of the movement target partial color space P1. The point sequence on the radius R1 may be moved so long as the order of the point sequence after the movement is not changed.
[0065]
Assuming that the position vector of the point X is “↑ AX” and the position vector after the movement is “↑ AZ”, the destination to which the point X is moved is represented by Expression (9). Note that the point A has been translated in parallel to the origin, as in the case of the partial color adjustment, and is a "$ 0" vector.
(Equation 9)

[0066]
Also, “↑ AZ” in which “↑ AX” has been moved in this way is expressed as a point R0 ′. One stage ends when this point R0 'is found. In the second stage, the same movement as in the above-described partial color adjustment may be performed on the point R0 '. If this two-step process is described in a summarized form, it is expressed by equation (10).
(Equation 10)

[0067]
The above is the description of the principle of the convergent partial color adjustment. Since the portion to which the convergent partial color adjustment is applied is part of the original conversion target area P, it is almost impossible for phenomena such as color skipping and gradation reversal to occur at the boundary portion outside the adjustment target area. It is as follows.
[0068]
In addition, both the partial color adjustment and the convergent partial color adjustment have been described in the case where the target color space is multidimensional. However, the present invention can be applied to a so-called one-dimensional color space such as a monochrome image. .
[0069]
FIG. 7 is a block diagram illustrating an embodiment of an image processing apparatus that performs the above-described partial color adjustment method. As described above, the color space for performing the partial color adjustment may be any color space, but in the present embodiment, the color space defined by the CIE is L ^* a ^* b ^* Color space. However, the present invention is not limited to this. For example, it is defined by a device-dependent color space such as a display RGB or a scanner RGB using red R, green G, and blue B (collectively referred to as RGB), or specified by CIE. L ^* u ^* v ^* It is also possible to use color signals on a device-independent color space, which is a color space that does not depend on the device of expression. Of course, the partial color adjustment unit 20 may handle any of various other device-dependent color spaces and various device-independent color spaces as signals to be color-adjusted.
[0070]
The image processing apparatus 1 according to the present embodiment includes, for example, an image input unit 3 that captures input image data represented in an RGB color section, and outputs a color signal Sin of the input image data to L. ^* a ^* b ^* For each color point in the conversion target area P defined by the color conversion unit 10 that converts the color signal into a color signal in the space, and the target partial color space P1 and the destination partial color space P2, the color coordinates are calculated as described above. A partial color adjustment unit 20 that is an example of a color coordinate movement unit that performs partial color adjustment by moving, and a partial color adjustment unit that is an example of a movement parameter setting unit that sets a movement parameter in the partial color adjustment unit 20 A color adjustment parameter acquisition unit 30;
[0071]
Further, the image processing apparatus 1 performs the L adjustment of the color by the partial color ^* a ^* b ^* A color conversion unit 40 for returning a color signal in the space to an original color signal in the RGB color space, and a color signal from the color conversion unit 40 to an external image output device such as a printer, a CRT, or an LCD (liquid crystal). And an image data output unit 5 for outputting the image data.
[0072]
The color conversion unit 10, the partial color adjustment unit 20, the partial color adjustment parameter acquisition unit 30, and the color conversion unit 40 constitute one embodiment of the color adjustment device 400 according to the present invention.
[0073]
Since the color conversion processing in the color conversion units 10 and 40 is a known technique, a detailed description is omitted. The partial color adjustment unit 20 has a coefficient acquisition unit 22 that acquires a color conversion coefficient. As described above, the coefficient obtaining unit 22 obtains, as the color conversion coefficient, the coefficient of the vector indicating the movement of the color coordinates.
[0074]
Prior to actual partial color adjustment, a parameter relating to partial color adjustment is acquired by the partial color adjustment parameter acquisition unit 30. The parameter acquisition will be described later. Parameters relating to the partial color adjustment are set in the partial color adjustment unit 20. Further, prior to the actual image processing, the input image ^* a ^* b ^* A color conversion coefficient for converting to a color signal is set.
[0075]
When the color conversion unit 40 sets the inverse conversion of the color conversion by the color conversion unit 10, the output image finally obtained is an image obtained by performing only the change by the partial color adjustment. If output to a printer is performed after performing the partial color adjustment, a color conversion coefficient for converting to a color signal such as CMYK for a printer may be set. ^* a ^* b ^* If an image signal is to be retained, it is possible to select not to perform color conversion by the color conversion unit 40, and an appropriate color conversion coefficient may be set.
[0076]
In this way, after the preparation is completed, the input image is sequentially converted to L ^* a ^* b ^* It is converted to a color signal. The next partial color adjustment unit 20 performs a desired adjustment and adjusts the adjusted L within the adjustment target area P. ^* a ^* b ^* If the color signal is not the L signal input to the partial color adjustment unit 20, ^* a ^* b ^* The color signal is output as it is. Details of the internal operation of the partial color adjustment unit 20 will be described later. Next, a desired color conversion is performed in the color conversion unit 40, and output image data is generated. This output image data is output via the image data output unit 5 to a display device, a printing device, or the like.
[0077]
FIG. 8 is a block diagram illustrating a detailed configuration example of the partial color adjustment unit 20 in the image processing apparatus 1 according to the present embodiment. As shown in the figure, the partial color adjustment unit 20 outputs the L input from the color conversion unit 10. ^* a ^* b ^* The primary area inside / outside determination unit 210 that determines whether the pixel data indicated by the color signal is inside or outside the primary area, and is inside (may include a boundary) by the primary area inside / outside determination unit 210. And a movement processing unit 220 that performs a predetermined parallel movement or rotation movement on the pixel data determined to be. L subjected to movement processing by the movement processing unit 220 ^* a ^* b ^* If the color signal is ^* a ^* b ^* A) One color signal. In addition, L which is not subjected to parallel movement or rotational movement ^* a ^* b ^* The color signal is expressed as (L ^* a ^* b ^* ) 0 color signal. The translation or rotation of the primary region is L ^* a ^* b ^* And a known technique may be used. Here, the detailed description is omitted.
[0078]
Further, the partial color adjustment unit 20 has been subjected to the parallel movement and the rotation movement from the movement processing unit 220 (L ^* a ^* b ^* ) The one-color signal and the parallel or rotational movement from the primary area inside / outside determination unit 210 are not applied (L ^* a ^* b ^* ) With respect to the 0 color signal, the secondary area inside / outside determination unit 230 that determines whether the pixel data indicated by each color signal is inside or outside the conversion target area P, and based on the above-described principle of partial color adjustment A partial color adjustment conversion unit 240 including a coefficient acquisition unit 22 for performing a desired partial color adjustment, and a movement inverse conversion processing unit for performing an inverse conversion of a rotational movement and an inverse conversion of a parallel movement performed by the movement processing unit 220 250.
[0079]
The secondary area inside / outside determination unit 230 determines (L) from the primary area inside / outside determination unit 210 when it determines that it is outside when performing the inside / outside determination. ^* a ^* b ^* ) The 0 color signal is output to the color conversion section 40 as it is. On the other hand, when it is determined that the position is inside (the boundary may be included), (L ^* a ^* b ^* 1) Send one color signal to the partial color adjustment conversion unit 240. The partial color adjustment conversion unit 240 performs a desired partial color adjustment based on the principle of the partial color adjustment, and sends it to the movement inverse conversion processing unit 250. The inverse movement conversion processing unit 250 performs the inverse conversion of the rotational movement and the inverse conversion of the parallel movement performed by the movement processing unit 220, and sends the L to the next-stage color conversion unit 40. ^* a ^* b ^* Outputs color signals.
[0080]
FIG. 9 is a diagram illustrating a primary area handled by the primary area inside / outside determination unit 210. In the figure, L ^* , A ^* , B ^* The input color space is shown for each axis, and shows the state of the adjustment target area (conversion target area) P before the cylinder performs parallel movement and rotational movement. L that almost completely contains this cylinder ^* , A ^* , B ^* A rectangular parallelepiped that is parallel to each axis is obtained, and this is defined as a primary region. This rectangular parallelepiped includes a cylindrical adjustment target region P, and is preferably as small as possible. L ^* a ^* b ^* Determining whether or not the color signal is inside the rectangular parallelepiped is the primary area inside / outside determination. The inside / outside determination for such a rectangular parallelepiped is extremely simple, and is highly effective in reducing the processing time. When the primary area is determined to be outside in the primary area inside / outside determination, the primary area inside / outside determination section 210 outputs the L input from the color conversion section 10 to the partial color adjustment section 20. ^* a ^* b ^* The color signal is output to the color conversion section 40 as it is.
[0081]
FIG. 10 is a diagram illustrating an example of the configuration of the partial color adjustment parameter acquisition unit 30, and illustrates a user interface screen. For example, parameters are obtained by an operator input from a user interface such as a keyboard and a mouse.
[0082]
The partial color adjustment parameter acquiring unit 30 specifies the shapes of the movement target partial color space P1 and the movement destination partial color space P2 based on an instruction from the operator. For example, the operator specifies the shape of the movement target partial color space P1 or the movement destination partial color space P2 and the center coordinates according to the shape. In response, the partial color adjustment parameter acquisition unit 30 specifies each region shape. The partial color adjustment unit 20 specifies the conversion target area P based on the area information and performs the above-described partial color adjustment.
[0083]
In order to receive a user instruction for specifying such a moving target partial color space P1 or a moving destination partial color space P2, the display screen is formed as shown in FIG. , A dialog box 320 for inputting the center coordinates of the target sub-color space P1 and the center coordinates of the destination sub-space, depending on the shapes of the target sub-color space P1 and the destination sub-space Dialog box 330 for inputting parameters relating to partial color adjustment, L ^* a ^* b ^* It has a dialog box 340 for specifying a color chart in a color space, a color chart display area 350 for displaying a color chart, and an image display area 360 for displaying an input image.
[0084]
One of the parameters relating to the partial color adjustment is the shape of the movement target partial color space P1 and the movement destination partial space. In the figure, a dialog box 310 is used to select the shape of the movement target partial color space P1 and the movement destination partial space. The initial value is a sphere.
[0085]
The parameters related to the partial color adjustment depending on the shapes of the moving target partial color space P1 and the moving destination partial space are the moving target partial color space P1 and the radius of the moving destination partial space shown in the dialog box 330. The figure shows a dialog box when a sphere is selected. When an ellipsoid is selected in the dialog box 310, the dialog box is switched to a dialog box for inputting a radius in three directions. The initial value is automatic, and if automatic is selected, if the object is a sphere, the radius is automatically calculated from the distance between the center coordinates of the movement target partial color space P1 and the center coordinates of the movement destination subspace determined thereafter. Is determined to be half of the distance between the center coordinates. The same applies to the case of a cylinder.
[0086]
If an ellipsoid is selected, it is regarded as a sphere, which is the same as the automatic operation when a sphere is selected. In other words, the partial color adjustment parameter acquiring unit 30 uses the dialog box 310 to change the radius of the spherical shape if the shape of the moving target partial color space P1 or the moving destination partial color space P2 is spherical. In the case of, the size of a shape corresponding to designating a radius for a sphere is specified.
[0087]
The remaining parameters relating to the partial color adjustment are the center coordinates of the movement target partial color space P1 and the center coordinates of the movement destination partial space. By the dialog box 320 in the figure, L ^* a ^* b ^* You can enter color space coordinates. Where L ^* a ^* b ^* Since the coordinate values of the color space are difficult to perceive intuitively, a predetermined color chart is displayed in the color chart display area 350 in the figure, and the operator visually checks and clicks with a pointing member such as a mouse to set the coordinate values. May be obtained.
[0088]
In the drawing, the source coordinates of the dialog box 320 indicate the center coordinates of the target partial color space P1, and the destination coordinates indicate the center coordinates of the destination subspace. A dialog box 320 in the figure indicates that the input of the movement source coordinates is active. In the case of input from a color chart, in this example, the L of the color chart is added to the source coordinates. ^* a ^* b ^* The coordinate values of the color space are displayed, and operations such as changing some values are also possible.
[0089]
Also, L ^* a ^* b ^* Since it is difficult to display all the color charts in the color space, a part of the color solid shown in the dialog box 340 in the figure is clicked with the mouse to display the same hue plane or the same lightness plane including the part. Are displayed as actual color patches (color patch display area 350 in the figure). The data corresponding to this color chart is L ^* a ^* b ^* In the case of displaying a color chart, which is data of a color space, color conversion is performed on a display RGB for display and display is performed. This color conversion uses a display ICC (International Color Consortium) profile.
[0090]
In general, the colors on the display cannot be displayed so precisely, ^* a ^* b ^* After the color conversion into the color space, the color conversion is performed using the same ICC profile as the color chart display. That is, the display color of the RGB color space on the display and L ^* a ^* b ^* Even if the value matching accuracy is not so good, the user can compare the image and the color chart under the same condition.
[0091]
Also, the center coordinates can be input by clicking on the display image. That is, the operator may click on the image or select and click on the color chart. In addition, when all parameters are determined, although not shown, the preview button is used to display an image when the display image is partially adjusted, and if it is desired to return to the state before the preview, A preview cancel button is used to return to the previous display image. After the setting or preview is completed, the setting is completed by clicking a setting end button (not shown).
[0092]
Although not shown, a user interface screen relating to convergent partial color adjustment can also be selected. In this case, a dialog box for inputting the ratio of the size of the convergent area to the movement target partial color space P1 is merely added to the above-described partial color adjustment. The size ratio is “0” or more and “1” or less.
[0093]
In the image processing apparatus 1 having the above configuration, the color is adjusted by receiving the user's specification. However, the present invention is not limited to this. In this case, there is no need for the operator to set parameters relating to partial color adjustment via the user interface. Examples of the automatic adjustment include, for example, preferable reproduction of a memory color. Human skin color, blue sky, green grass, etc. are said to be memory colors. ^* a ^* b ^* There is a color signal whose color corresponding to the center coordinate of the destination subspace is known. In such a case, the color distribution of the image is checked using a three-dimensional histogram or the like in the color space of the image data, and if there is a color that is close to the memory color, it is set as the center coordinate of the partial color space P1 to be moved. Is determined, and partial color adjustment can be performed so as to approach a preferable reproduction.
[0094]
As a more preferable method, especially in the case of skin color, not only the color distribution but also a method such as face recognition as to whether or not a person's face exists in the image is extracted, and the skin color region in the image is extracted and extracted. Processing such as viewing the color distribution may be performed only on the selected area, and partial color adjustment may be performed.
[0095]
It is also an effective means for removing the base. For example, if there is a document and image data is acquired by an image pickup system such as a scanner or a digital camera, what should be reproduced in a uniform color such as paper white or a color chart, that is, the pixel value of the image data There is a case where what should be a constant value actually has a certain distribution (variation). It is preferable to apply the convergent partial color adjustment described above to such image data in order to make the color information of the background part a constant value.
[0096]
In particular, in the case of compressing image data in which variations should occur in the image data that should be uniform, the effect of the convergent partial color adjustment is very large, for example, the compression ratio may be significantly increased. . As described above, even when this convergent partial color adjustment is applied, phenomena such as color jump and gradation inversion hardly occur at the boundary between the original conversion target region P and the outside of the adjustment target region. is there.
[0097]
FIG. 11 is a diagram illustrating a color conversion definition for color conversion using the above-described partial color adjustment method. Here, the color conversion definition has the same meaning as the color conversion coefficient expressed in the image processing apparatus 1.
[0098]
The color conversion definition defines a correspondence from the input color space to the output color space, and mathematically indicates a function having a functional relationship. Actually, it is a table value of a one-dimensional lookup table (LUT), a table value of a multi-dimensional LUT (DLUT; multi-dimension LUT), and a value of a matrix element, and is realized by a combination thereof. These values are collectively called a profile. The most common example of the color conversion definition is an ICC profile established by the ICC. In particular, the case of the DLUT is effective in combination with the above-described partial color adjustment. The DLUT is composed of regular multidimensional (three-dimensional in the figure) grid points using the input color space as addresses, as shown in FIG. 11A, for example. Is stored.
[0099]
When an input value located at a grid point comes in, the value at that grid point is used as an output value. On the other hand, when an input value located between grid points is input, interpolation is performed with reference to neighboring grid points to obtain an output value. This is because changing the output values of some of the grid points does not affect the whole.
[0100]
Here, if the data value of the grid point is changed, the output color value is changed. That is, by editing specific grid point data in such a look-up table, it is possible to partially adjust the color only for a specific color. Also, for example, as shown in FIG. 11B, if a convergent area including a plurality of grid points such as grid points J1, J2, J3, and J4 is set, and the values of the grid points in the area are all the same, The above-mentioned convergent partial color adjustment can also be realized. That is, if all the points in the region centered on the grid points J1, J2, J3, and J4 in FIG. 11B have the same color value, the input color corresponding to the grid points J1, J2, J3, and J4 is obtained. All the input color values can be moved to the same color value, and the other input color values maintain the continuity of the gradation at the boundary with the outside of the adjustment target area by the above-described partial color adjustment, and perform the color inversion. Partial color adjustment can be performed to prevent
[0101]
FIG. 11B shows a preferred example of a two-dimensional LUT, in which the convergence area is defined by grid points J1, J2, J3, and J4 that form a square grid. It is not necessarily required to be square, and may be rectangular. The number of grid points for defining the convergence area is not necessarily limited to “4”, but may be at least “2” or more. For example, if the number is “3”, the area surrounded by the triangle converges. Area. If “2” is set, a certain range in one direction becomes a convergence area.
[0102]
In the case of a three-dimensional LUT, a range defined by eight grid points in a square grid is preferably set as a convergent area. Of course, also in this case, the number of grid points for defining the convergence area is not necessarily limited to “8”, but may be at least “2” or more. Are three-dimensionally arranged, an area surrounded by triangulation becomes a convergence area.
[0103]
FIG. 12 is a block diagram illustrating an embodiment of a profile editing apparatus that performs editing of a color conversion definition by using the above-described partial color adjustment method. The profile editing device 2 edits a previously prepared color conversion definition by using the above-described partial color adjustment for the color conversion definition for color conversion.
[0104]
The profile editing device 2 edits at least a profile including a DLUT. That is, a color conversion coefficient is obtained by using the above-described partial color adjustment, and the obtained color conversion coefficient is replaced with a coefficient of the color conversion definition prepared in advance, thereby obtaining an input profile which is an example of the color conversion definition. Edit. For example, the above-described partial color adjustment is performed on a profile created in advance by the profile generation device, and a change is made to a part of the profile, that is, an output value stored in some grid points of the DLUT. In this embodiment, the output value of the DLUT is L ^* a ^* b ^* An example will be described in which the data is color space data.
[0105]
As shown in FIG. 12, the profile editing device 2 obtains the input profile obtained by the profile generating device, and obtains the color coordinates of each color point in the conversion target area P as described above. A profile editing unit 70 that is an example of a color coordinate moving unit that performs partial color adjustment by moving, and a partial color adjustment parameter acquisition that is an example of a movement parameter setting unit that sets a movement parameter in the profile editing unit 70 A profile output unit that returns the output profile edited by the profile editing unit to the profile generation device. The profile editing unit 70 includes a coefficient acquisition unit 72, like the partial color adjustment unit 20.
[0106]
The profile editing unit 70 and the partial color adjustment parameter obtaining unit 80 constitute one embodiment of the color adjustment device 400 according to the present invention.
[0107]
In this configuration, the profile editing device 2 acquires the partial color adjustment parameters by the partial color adjustment parameter acquisition unit 80 before changing the input profile acquired by the input profile acquisition unit 60. The partial color adjustment parameter acquisition unit 80 sets the acquired partial color adjustment parameters in the profile editing unit 70. The profile editing unit 70 edits the input profile acquired by the input profile acquisition unit 60 based on the set partial color adjustment parameters. The edited profile is sent as an output profile to the profile generation device via the output profile sending unit 90.
[0108]
The DLUT may be considered to be equivalent to the color chart image data. In such a case, it is basically necessary to perform the same partial color adjustment as described in the image processing apparatus 1. However, since the grid points only intermittently exist in the color space, the center coordinates of the movement target partial color space P1 are stored in the grid points. ^* a ^* b ^* The value can be expected to be more effective. Of course, a value between grid points may be used, but in the present embodiment, grid points can be designated.
[0109]
FIG. 13 is a diagram illustrating a configuration example of the partial color adjustment parameter acquisition unit 80, and illustrates a user interface screen. For example, parameters are obtained by an operator input from a user interface such as a keyboard and a mouse.
[0110]
As illustrated, the partial color adjustment parameter acquisition unit 80 generates a user interface screen substantially similar to the partial color adjustment parameter acquisition unit 30 in the image processing apparatus 1. As shown in the figure, a dialog box 810 for receiving designation of the shape of the movement target partial color space P1 and the shape of the movement destination subspace, and a dialog box for inputting the center coordinates of the movement target partial color space P1 and the center coordinates of the movement destination subspace 820, a dialog box 830 for inputting parameters related to partial color adjustment depending on the shapes of the movement target partial color space P1 and the movement destination partial space 830, L ^* a ^* b ^* It has a dialog box 840 for specifying a color chart in a color space, and a color chart display area 850 for displaying the color chart. These are the same as the display screen generated by the partial color adjustment parameter acquisition unit 30.
[0111]
The display screen displays the input profile as a ^* -B ^* Plane, L ^* -A ^* Plane, L ^* -B ^* It has a profile display area 360 for displaying three planes, and a dialog box 870 for specifying a color chart for the DLUT. These two points are different from the display screen generated by the partial color adjustment parameter acquisition unit 30.
[0112]
The dialog box 870 in the figure for selecting a color chart to be displayed displays the DLUT in the read profile because the target is the DLUT. Therefore, the user may see a ^* -B ^* Plane, L ^* -A ^* Plane, L ^* -B ^* One of three planes is selected. The color chart displayed in the color chart display area 850 is obtained by converting grid points of the DLUT into color charts. Note that the dialog box 840 and the dialog box 870 cannot be selected at the same time. The dialog box 840 can also be used to set the center coordinates between grid points, and can be used to specify the center coordinates of the movement target partial color space P1 and the center coordinates of the movement destination partial space.
[0113]
Further, since what is input to the profile editing device 2 is a profile, a profile display area 860 is provided in a portion that was the image display area 360 in the image processing device 1 in the illustrated screen example. In the profile display area 860, a ^* -B ^* Plane, L ^* -A ^* Plane, L ^* -B ^* A profile is displayed in a continuous tone by interpolating between lattice points on three planes. With this display, the user can confirm whether or not an unnatural profile is obtained by performing extreme editing when previewing.
[0114]
Although not shown, a user interface screen relating to convergent partial color adjustment can also be selected. In this case, a dialog box for inputting the ratio of the size of the convergent area to the movement target partial color space P1 is merely added to the above-described partial color adjustment. The size ratio is “0” or more and “1” or less. This is also the same as the partial color adjustment parameter acquisition unit 30 in the image processing apparatus 1.
[0115]
Also, the above-mentioned convergent partial color adjustment can be applied to the color conversion definition. By designating a plurality of DLUT lattice points as the convergence area, a constant color can be obtained at the DLUT lattice points that generally belong to the convergence area. For example, as shown in the convergent partial color adjustment in the image processing apparatus 1, an effect of removing the background can be added to the color conversion definition. Also, the color conversion definition is converted from the RGB color space to L ^* a ^* b ^* As a color conversion using a DLUT to a color space, the inverse conversion of the color conversion definition is defined as the color conversion definition, ^* a ^* b ^* Color conversion using a DLUT from a color space to an RGB color space can also be performed.
[0116]
In this case, the input RGB is once set to L by the color conversion definition. ^* a ^* b ^* After the conversion to the color space, output RGB is generated with another color conversion definition. It is expected that the input RGB and the output RGB are substantially the same. However, it is often the case that whether the R, G, B single colors in the input RGB are the single colors in the output RGB is not necessarily the same. This is because L in the color conversion definition for the output RGB ^* a ^* b ^* This is because grid points are created irrespective of the color conversion definition for input RGB. If it is desired that the output RGB be monochromatic when the input RGB is monochromatic, convergent partial color adjustment adjustment is performed on an appropriate grid point of the color conversion definition for output RGB, and the color conversion for output RGB is performed. It is effective to make the definition output value a single color.
[0117]
FIG. 14 is a block diagram illustrating an embodiment of an image processing system that performs color conversion using the output profile edited by the profile editing device 2 described above. As shown, the image processing system 9 includes an image processing device 1, a profile editing device 2, and a profile generation device 500. The profile editing device 2 is the same as that described in the above embodiment.
[0118]
In the above-described image processing apparatus 1, by obtaining the converted color coordinate values one by one using the individual color coordinate values of the input image as the colors to be converted, a specific color in the input image is partially converted into another color. Although color conversion into colors is possible, such sequential processing is time-consuming and impractical. On the other hand, the profile editing device 2 previously edits an input profile composed of coefficients for color gamut conversion (color conversion coefficients), and converts the input image into a color gamut using the edited output profile. This is the image processing system 9.
[0119]
The profile editing device 2 edits the color conversion coefficient on the input profile (specifically, the look-up table) generated by the profile generation device 500 using the above-described partial color adjustment processing. It is as follows. The profile editing device 2 returns an output profile composed of the edited color gamut conversion coefficients to the profile generation device 500. The profile generation device 500 writes the output profile received from the profile editing device 2 in the storage medium 28 provided in the image processing device 1.
[0120]
That is, the storage medium 28 stores color conversion coefficients for color conversion edited using the above-described partial color adjustment processing. At this time, the relationship between the input color coordinate values and the output color coordinate values within the color gamut to be adjusted of the input image is stored in the storage medium 28 in a multidimensional conversion table used for color gamut conversion of the input image. Store as grid point data. The image processing device 1 performs color gamut conversion on the input image by using the grid point data and the interpolation operation.
[0121]
FIG. 14 shows an example in which the input image signal Sin is RGB data and the converted data is input to a color display 7 which is an example of a color image output device. The input image signal Sin of the RGB data is input to the color conversion unit 10 via the image input unit 3. Then, the color conversion unit 10 ^* a ^* b ^* Converted to data, and the converted L ^* a ^* b ^* The data is supplied to the partial color adjustment unit 20.
[0122]
As shown in the figure, the partial color adjustment unit 20 and the color conversion unit 40 of the above embodiment are configured by a three-dimensional table 25, an interpolation operation unit 26, and one-dimensional tables 27r, 27g, 27b. Stores lattice point data of RGB data edited by the profile editing device 2 described above in advance. The storage medium 28 is constituted by the three-dimensional table 25 and the one-dimensional tables 27r, 27g, 27b.
[0123]
Then, L from the color conversion unit 10 ^* a ^* b ^* The three-dimensional table 25 is indexed by the high-order bits of the data, grid point data is read from the three-dimensional table 25, and the read grid point data is input to the interpolation calculating unit 26 by the L ^* a ^* b ^* Interpolation is performed using the lower bits of the data, and RGB data Ri, Ci, Bi after color gamut conversion are obtained from the three-dimensional table 25.
[0124]
Known interpolation methods include, for example, a method of dividing a unit cube into six triangular pyramids and performing an interpolation operation, a method of dividing a unit cube into two triangular prisms and performing an interpolation operation, and a method of directly interpolating a unit cube into a unit cube. Interpolation processing may be applied.
[0125]
As described above, since the color after color gamut conversion is obtained by the interpolation calculation of the grid point data, points generated outside the color gamut of the input image are also included as grid points when generating or editing the grid point data. Therefore, the RGB data Ri, Ci, Bi obtained from the three-dimensional table 25 as the colors after the color gamut conversion include colors outside the display reproduction range.
[0126]
Therefore, the RGB data Ri, Gi, Bi from the three-dimensional table 25 are converted by the one-dimensional tables 27r, 27g, 27b without correcting as much as possible the color signals in the display color gamut as the reproduction destination device and outside the display color gamut. The color signal is subjected to a color gamut mapping process so that the inversion of the saturation does not occur as much as possible, and the RGB data Ro, Go, Bo after the color gamut mapping process are output to the display 7.
[0127]
In the above-described embodiment, the functional parts of the partial color adjustment unit 20 and the profile editing unit 70 are described as being configured by hardware. However, the present invention is not limited to this, and a CPU (Central Processing Unit) such as a microcomputer The above-described processing functions can be realized by software using a so-called electronic computer such as a personal computer or a personal computer.
[0128]
In this case, an electronic computing device such as a microcomputer or a personal computer includes each functional unit such as the above-described partial color adjustment parameter acquisition unit 30 and profile editing unit 70 as software. That is, from a storage medium (eg, a RAM (not shown)) recording software program codes for realizing the respective functional parts such as the above-described partial color adjustment parameter acquisition unit 30 and profile editing unit 70, the computer (or CPU or CPU) of the apparatus. The effects described in the above embodiments are achieved by the MPU) reading and executing the program code. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment. The program is not limited to the program provided via the storage medium, but may be a program obtained by downloading program data distributed via a wired or wireless communication unit.
[0129]
Each function is realized not only by executing the program code read out by the computer, but also by an OS (Operating System) running on the computer based on an instruction of the program code. It may be a case where all or some of the units are performed and each function is realized by the processing. Further, after the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function expansion card is written based on the instruction of the program code. Or a CPU or the like provided in the function expansion unit may perform part or all of the actual processing, and the processing may realize the functions of the above-described embodiments.
[0130]
As described above, the present invention has been described using the embodiment. However, the technical scope of the present invention is not limited to the scope described in the embodiment. Various changes or improvements can be made to the above-described embodiment without departing from the spirit of the invention, and embodiments with such changes or improvements are also included in the technical scope of the present invention.
[0131]
Further, the above embodiments do not limit the invention according to the claims (claims), and all combinations of the features described in the embodiments are not necessarily essential to the means for solving the invention. Absent. The embodiments described above include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. Even if some components are deleted from all the components shown in the embodiment, as long as the effect is obtained, a configuration from which some components are deleted can be extracted as an invention.
[0132]
【The invention's effect】
As described above, according to the present invention, within the range of the adjustment target area, the continuity of the gradation is maintained, and the color in the adjustment target area is compared with the input color space without causing color inversion. A coefficient for converting to another color on the output color space which is the same color space is obtained. In other words, when the color coordinates of a specific area are moved to a certain area in the color space to be adjusted, the gradation and color continuity are not impaired at the boundary with the non-moving area. Partial color adjustment can be performed without causing image quality defects such as inversion.
[0133]
Therefore, by treating the conversion target area defined as the area connecting the movement target partial color space and the movement destination partial color space as the adjustment target color space, the restriction on the inclusive relation, which has been a restriction in the conventional method, is reduced. Can be removed. Thus, for example, the center and radius of the color to be moved or the center and radius of the destination can be given independently, and the degree of freedom in color adjustment increases. Further, a selective color adjustment function having a high degree of freedom can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating the relationship between a target partial color space to be processed, a destination partial color space, and a color space to be adjusted in one embodiment of the color adjustment method according to the present invention.
FIG. 2 is a diagram illustrating weighting at the time of color adjustment.
FIG. 3 is a diagram illustrating color adjustment when the shape of a conversion target area is cylindrical.
FIG. 4 is a diagram for explaining color adjustment when the adjustment target area has a capsule shape.
FIG. 5 is a diagram illustrating color adjustment when the movement target partial color space and the movement destination partial color space have a similar relationship.
FIG. 6 is a diagram illustrating convergent partial color adjustment.
FIG. 7 is a block diagram illustrating an embodiment of an image processing apparatus that performs a partial color adjustment method.
FIG. 8 is a block diagram illustrating a detailed configuration example of a partial color adjustment unit in the image processing apparatus.
FIG. 9 is a diagram illustrating a primary area handled by a primary area inside / outside determination unit.
FIG. 10 is a diagram illustrating a user interface screen generated by a partial color adjustment parameter acquisition unit in the partial color adjustment unit.
FIG. 11 is a diagram illustrating a color conversion definition for color conversion using a partial color adjustment method.
FIG. 12 is a block diagram illustrating one embodiment of a profile editing device that implements a color conversion definition using a partial color adjustment method.
FIG. 13 is a diagram illustrating a user interface screen generated by a partial color adjustment parameter acquisition unit in the profile editing device.
FIG. 14 is a block diagram illustrating an embodiment of an image processing system that performs color conversion using an output profile edited by a profile editing device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image processing apparatus, 2 ... Profile editing apparatus, 3 ... Image input part, 5 ... Image data output part, 10, 40 ... Color conversion part, 20 ... Partial color adjustment part, 22, 72 ... Coefficient acquisition part, 30 ... partial color adjustment parameter acquisition unit, 60 ... input profile acquisition unit, 70 ... profile editing unit, 80 ... partial color adjustment parameter acquisition unit, 90 ... output profile transmission unit, 210 ... primary area inside / outside determination unit, 220 ... Movement processing unit, 230 ... secondary area inside / outside determination unit, 240 ... partial color adjustment conversion unit, 250 ... movement inverse conversion processing unit, 310, 320, 330, 340 ... dialog box, 350 ... color chart display area, 360 ... image Display area, 810, 820, 830, 840, 870: Dialog box, 850: Color chart display area, 860: Profile display area, P: Conversion target area, P0 Adjust the target color space, P1 ... moving target partial color space, P2 ... destination partial color space

Claims (30)

A color adjustment method for obtaining a coefficient for performing color conversion from an input color space to an output color space for a predetermined adjustment target area in a color space to which a color image belongs,
Within the range of the adjustment target area, the output color which is in the same color space as the input color space, while maintaining the continuity of gradation and without causing color inversion, A color adjustment method characterized by finding a coefficient for converting to another color in space. The adjustment target area inscribes or includes a movement target partial color space including a color to be subjected to the color conversion processing and a movement destination partial color space including a color corresponding to the obtained coefficient. The color adjustment method according to claim 1, wherein the color adjustment method is included. Determine a representative color representing the color of the movement target partial color space and a target color that is a target color after the color conversion process representing the color of the destination partial color space, and determine the target color from the representative color. A basic vector indicating the movement in the color space to the target color is obtained, and the image data included in the adjustment target area is moved in the color space according to the direction and the distance indicated by the basic vector, and the adjustment target area and the adjustment target are adjusted. 3. The color adjustment method according to claim 2, wherein the amount of the movement is substantially zero at a boundary with the region. Coordinate transformation by rotational movement such that a straight line connecting the representative color of the movement target partial color space and the target color of the movement destination partial color space is parallel to one of the color space coordinate axes indicating the adjustment target area. Performing the step of
Performing the color conversion process on the adjustment target area;
4. The method according to claim 3, further comprising the step of: performing a reverse transformation of the coordinate transformation by the rotational movement. A primary area is set to almost completely include the adjustment target area in the input color space, and it is determined whether the pixel data indicated by the input color signal is inside or outside the primary area. A primary area inside / outside determination step;
A straight line connecting the representative color of the target partial color space and the target color of the destination partial color space with respect to the pixel data determined to be inside the primary region in the primary region inside / outside determination step. Performing a coordinate transformation by rotational movement so as to be parallel to any of the color space coordinate axes indicating the adjustment target area,
Regarding the color signal that has been subjected to the rotational movement and the color signal that has not been subjected to the rotational movement in the step of performing the coordinate transformation, pixel data indicated by each color signal is inside or outside the adjustment target area. A secondary area inside / outside determination step of determining whether there is a
Performing a color conversion process on the pixel data determined to be inside the adjustment target region in the secondary region inside / outside determination step;
5. The color adjustment according to claim 3, further comprising the step of: performing a reverse transformation of the coordinate transformation by the rotational movement on the pixel data subjected to the color transformation in the step of performing the color transformation process. Method. Targeting the representative color of the movement target partial color space or the target color of the movement destination partial color space, performing coordinate conversion by parallel movement to the origin of a color space coordinate axis indicating the adjustment target area;
Performing the color conversion process on the adjustment target area;
The method according to claim 3, further comprising: performing a reverse transformation of the coordinate transformation by the parallel movement. A primary area is set to almost completely include the adjustment target area in the input color space, and it is determined whether the pixel data indicated by the input color signal is inside or outside the primary area. A primary area inside / outside determination step;
For the pixel data determined to be inside the primary area in the primary area inside / outside determination step, with respect to the representative color of the movement target partial color space or the target color of the movement destination partial color space, Performing a coordinate transformation by parallel movement to the origin of the color space coordinate axis indicating the adjustment target area;
Regarding the color signal subjected to the translation and the color signal not subjected to the translation in the step of performing the coordinate transformation, pixel data indicated by each color signal is inside or outside the adjustment target area. A secondary area inside / outside determination step of determining whether there is a
Performing a color conversion process on the pixel data determined to be inside the adjustment target region in the secondary region inside / outside determination step;
A step of performing an inverse transformation of the coordinate transformation by the parallel movement with respect to the pixel data subjected to the color transformation in the step of performing the color transformation process. Item 2. The color adjustment method according to item 1. A convergence area is provided in a part of the range of the adjustment target area, and for the processing target part in the adjustment target area other than the convergence area, the continuity of gradation is maintained, and the color inversion is performed. The method according to claim 1, wherein the coefficient for converting a color in the adjustment target area into another color in the output color space that is the same color space as the input color space is obtained without generating the coefficient. 8. The color adjustment method according to any one of the seventh to seventh aspects. A color adjustment device that obtains a coefficient for performing color conversion from an input color space to an output color space for a predetermined adjustment target area in a color space to which a color image belongs,
Within the range of the adjustment target area, the output color which is in the same color space as the input color space, while maintaining the continuity of gradation and without causing color inversion, A color adjusting device, comprising: a coefficient obtaining unit that obtains the coefficient for converting to another color in space. The coefficient acquisition unit determines a representative color representing the color of the moving target partial color space and a target color that is a target color after the color conversion process representing the color of the moving destination partial color space. Calculating a basic vector indicating a movement in the color space from the representative color to the target color, moving the image data included in the adjustment target area in the color space according to the direction and the distance indicated by the basic vector, and performing the adjustment. 10. The color adjustment apparatus according to claim 9, wherein the amount of the movement is substantially zero at a boundary between the target area and the adjustment target area. Coordinate transformation by rotational movement such that a straight line connecting the representative color of the movement target partial color space and the target color of the movement destination partial color space is parallel to one of the color space coordinate axes indicating the adjustment target area. A movement processing unit for performing
A color adjustment conversion unit that performs the color conversion process on the adjustment target area;
The color adjustment apparatus according to claim 9, further comprising: an inverse transformation processing unit that performs an inverse transformation of the coordinate transformation by the rotational movement. A primary area is set to almost completely include the adjustment target area in the input color space, and it is determined whether the pixel data indicated by the input color signal is inside or outside the primary area. A primary area inside / outside determination unit,
A straight line connecting the representative color of the target partial color space and the target color of the destination partial color space for the pixel data determined to be inside the primary region by the primary area inside / outside determination unit. A movement processing unit that performs coordinate transformation by rotational movement so as to be parallel to any of the color space coordinate axes indicating the adjustment target area,
Regarding the color signal subjected to the rotational movement and the color signal not subjected to the rotational movement in the movement processing unit, whether the pixel data indicated by each color signal is inside or outside the adjustment target area A secondary area inside / outside determination unit for determining
A color adjustment conversion unit that performs the color conversion process on the pixel data determined to be inside the adjustment target area by the secondary area inside / outside determination unit;
11. The color according to claim 9, further comprising: an inverse conversion processing unit that performs an inverse conversion of the coordinate conversion by the rotational movement with respect to the pixel data color-converted by the color adjustment conversion unit. Adjustment device. A movement processing unit that performs a coordinate transformation by parallel movement to an origin of a color space coordinate axis indicating the adjustment target area with respect to the representative color of the movement target partial color space or the target color of the movement destination partial color space;
A color adjustment conversion unit that performs the color conversion process on the adjustment target area;
The color adjustment device according to claim 9, further comprising: an inverse transformation processing unit that performs an inverse transformation of the coordinate transformation by the parallel movement. A primary area is set to almost completely include the adjustment target area in the input color space, and it is determined whether the pixel data indicated by the input color signal is inside or outside the primary area. A primary area inside / outside determination unit,
For the pixel data determined to be inside the primary region by the primary region inside / outside determination unit, with respect to the representative color of the movement target partial color space or the target color of the movement destination partial color space, A movement processing unit that performs coordinate transformation by parallel movement to an origin of a color space coordinate axis indicating the adjustment target area;
Regarding the color signal subjected to the parallel movement and the color signal not subjected to the parallel movement by the movement processing unit, whether the pixel data indicated by each color signal is inside or outside the adjustment target area A secondary area inside / outside determination unit for determining
A color adjustment conversion unit that performs the color conversion process on the pixel data determined to be inside the adjustment target area by the secondary area inside / outside determination unit;
13. The image processing apparatus according to claim 9, further comprising: an inverse conversion processing unit that performs an inverse conversion corresponding to the coordinate conversion by the parallel movement with respect to the pixel data subjected to the color conversion by the color adjustment conversion unit. The color adjustment device according to any one of claims 1 to 4. At least one of the region of the movement target partial color space and the region of the destination partial color space is defined based on the shape of those regions and the center coordinates according to the shape of the region. The color adjustment device according to any one of claims 9 to 14, wherein At least one of the area of the movement target partial color space and the area of the destination partial color space has a shape of the sphere, a shape of an ellipsoid, a shape of a cylinder, a shape of an ellipse cylinder, and a shape of a rectangular parallelepiped. 16. The color adjustment device according to claim 15, wherein the color adjustment device is one of a shape and at least a closed three-dimensional shape that is not a torus shape. 17. The color adjustment device according to claim 9, wherein the coefficient acquisition unit sets a color space of a color signal handled in a process of obtaining the coefficient as a device-independent color space. . 17. The color adjustment apparatus according to claim 9, wherein the coefficient acquisition unit sets a color space of a color signal handled in a process of obtaining the coefficient as a device-dependent color space. The coefficient acquisition unit is provided with a convergence region in a part of the range of the adjustment target region, in the adjustment target region, for the processing target portion other than the convergence region, maintain the continuity of gradation, And calculating the coefficient for converting a color in the adjustment target area into another color in the output color space that is the same color space as the input color space without causing color inversion. The color adjustment device according to any one of claims 9 to 18, wherein By selecting a specified color patch from a plurality of color patches displayed on a predetermined display medium, the color coordinates of the representative color of the movement target partial color space and the color coordinates of the destination color space A movement parameter setting unit that specifies at least one of the color coordinates of the target color,
The color adjustment device according to claim 9, wherein the coefficient obtaining unit executes a process of obtaining the coefficient based on the color coordinates specified by the movement parameter setting unit. By receiving designation of a pixel point in the color image displayed on a predetermined display medium, the color coordinates of the representative color in the movement target partial color space and the color of the target color in the movement destination partial color space A movement parameter setting unit that specifies at least one of the coordinates,
The color adjustment device according to claim 9, wherein the coefficient obtaining unit executes a process of obtaining the coefficient based on the color coordinates specified by the movement parameter setting unit. A movement parameter setting unit that specifies at least one of the shape of the movement target partial color space and the shape of the movement destination partial color space,
22. The method according to claim 9, wherein the coefficient obtaining unit executes a process of obtaining the coefficient based on a shape of the color space specified by the moving parameter setting unit. A color adjustment device according to the item. A movement parameter setting unit that specifies the size of the shape corresponding to specifying a radius for a sphere according to at least one of the shape of the movement target partial color space and the shape of the movement destination partial color space With
The method according to claim 9, wherein the coefficient obtaining unit executes a process of obtaining the coefficient based on a size of the shape of the color space specified by the movement parameter setting unit. A color adjusting device according to any one of the preceding claims. A color conversion definition editing device for editing a color conversion definition composed of coefficients for performing color conversion from an input color space to an output color space for a predetermined adjustment target area in a color space to which a color image belongs,
A color adjusting device according to any one of claims 9 to 23,
A color conversion definition editing device, comprising: a coefficient editing unit that edits the color conversion definition by replacing the coefficient obtained by the coefficient obtaining unit with a coefficient of the color conversion definition prepared in advance. The coefficients constituting the color conversion definition are grid point data of a one-dimensional or multi-dimensional lookup table,
25. The color conversion definition editing apparatus according to claim 24, wherein the coefficient editing unit sets at least one of the grid points of the lookup table as the color coordinates of the representative color in the movement target partial color space. 20. A color adjusting device according to claim 19, wherein the color adjusting device provides a convergence region in a part of the range of the adjustment target region,
The coefficients constituting the color conversion definition are grid point data of a one-dimensional or multi-dimensional lookup table,
26. The color conversion definition editing apparatus according to claim 24, wherein the coefficient editing unit sets the convergence area so as to include two or more grid points of the lookup table. A specific color included in an input color image is converted into the another color by converting a certain color in a predetermined adjustment target area in a color space to which the color image belongs into another color in the same color space. An image processing device,
A color adjusting device according to any one of claims 9 to 23,
Based on the coefficient obtained by the coefficient obtaining unit, color conversion is performed by moving pixel data representing the color of each pixel included in the adjustment target area extracted from the input color image in the color space. An image processing apparatus comprising a partial color adjustment unit. A specific color included in an input color image is converted into the another color by converting a certain color in a predetermined adjustment target area in a color space to which the color image belongs into another color in the same color space. An image processing device,
A storage unit for storing a color conversion definition edited by the color conversion definition editing device according to any one of claims 24 to 26,
A partial color to be color-converted by converting pixel data representing a color of each pixel included in the adjustment target area extracted from the input color image based on the color conversion definition stored in the storage unit; An image processing device comprising an adjustment unit. A program for performing a process of obtaining a coefficient for performing color conversion from an input color space to an output color space for a predetermined adjustment target area in a color space to which a color image belongs,
Computer
Within the range of the adjustment target area, the output color which is the same color space as the input color space, while maintaining the continuity of gradation and without causing color reversal. A program for functioning as a coefficient obtaining unit for obtaining the coefficient for converting to another color in space. A computer-readable storage medium storing a program for performing a process of obtaining a coefficient for performing color conversion from an input color space to an output color space for a predetermined adjustment target area in a color space to which a color image belongs,
On the computer,
Within the range of the adjustment target area, the output color which is the same color space as the input color space, while maintaining the continuity of gradation and without causing color reversal. A storage medium storing a program for executing a procedure for obtaining the coefficient for converting to another color in space.

Images